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MICROBIOLOGY SND IMMUNOLOGY

LEARN THROUGH YOUR COURSE AND FORTIFY ALL YOUR WEAKNESS WITH KNOWLEDGE

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Topic 1: Objectives

At the end of this topic , the learner shall be able to:

    1. Define immunology
    2. .OUTLINE THE FUNCTIONS OF IMMUNE SYSTEM
    3. .OUTLINE THE ORGANS OF IMMUNE SYSTEM
    4. Describe the types of immunity

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Topic 1: introduction to imunology

  • •Immunology
    is the study of our protection from foreign macromolecules or invading organisms and our responses to them.
     •Host – e.g. me!!!!
                          •Foreign macromolecule, antigen – e.g. virus protein, worm, parasite (Everything                               that should not be in my body

    •Immune system = cells, tissues, and molecules that mediate resistance to infections
    •Immunology = study of structure and function of the immune system
    •Immunity = resistance of a host to pathogens and their toxic effects
    •Immune response = collective and coordinated response to the introduction of foreign substances in an individual mediated by the cells and molecules of the immune system
    • Role of immune system
    • Eliminate damaged or malignant cells

    •To protect humans from pathogenic microorganisms
    •Pathogenic microorganisms (Pathogens)
    –Microorganisms capable of causing infection and/or disease
    •Infection
    –Ability of pathogen to enter host, multiply and stimulate an immune response
    •Disease
    –Clinical manifestations associated with infection

    • Immunology is complex

    •Our Immune system involves the interplay between our Non-specific and our Specific Immune responses
    •Non-specific immunities collectively referred to as our Innate immunity
    •Specific immunities are referred to as our Adaptive immunity for which there are 2 branches: Humoral immunity and Cell-mediated immunity
    Organs Of Immune System
    •Primary Lymphoid Organs
      –Bone Marrow and Thymus
      –Maturation Site
    •Secondary Lymphoid Organs
      –Spleen, lymph nodes,
      –MALT (mucosal associated lymph tissue)
      –GALT (gut associated lymph tissue)
      –Trap antigen, APC, Lymphocyte Proliferation
    ORIGIN OF CELLS OF THE IMMUNE SYSTEM
    •Derived from common progenitor cell in bone marrow
      –Pluripotent hematopoietic stem cell
    •Progenitor Stem Cells
      –Erythroid lineage
    •Erythrocytes and Megakaryocytes
      –Myeloid lineage
    •Monocyte/macrophage, dendritic cells, PMN’s, mast cells
      –Lymphoid lineage
    •Small and large lymphocytes


    Central Immune organs
    Central Immune Organs are the sites of generation, differentiation and maturation of immunocytes.
      Bone marrow
      Thymus

HUMAN Lymphoid Organs


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Topic 1: immunology: types of immunity

Types Of Immunity

•Inborn or innate immunity: It is present at birth; This is our First Line Of Defense.
•Acquired or specific: It is not present at birth but becomes part of our immune system as the lymphoid system develops.
•1970: WHO defined immunity as immune response to antigen ( Foreign body) in form of
                  •Humoral ( activation of B-lymphocytes)
                  •Cellular (by activation of T-lymphocytes
1.Innate (non-adaptive)
–first line of immune response
–relies on mechanisms that exist before infection
2.Acquired (adaptive)
–Second line of response (if innate fails)
–relies on mechanisms that adapt after infection
–handled by T- and B- lymphocytes
–one cell determines one antigenic determinant
Distinction Between Innate and Adaptive Immune Responses
•Innate immunity is non-adaptive and helps to initiate adaptive immune responses (= first line of defense – but LIMITED)
  –Immediate (0-4 hours)
•Adaptive immunity provides a more universal line of defense and has long-lived memory to provide protection upon re-infection
  –Second line of defense
  –Generation of Ag-specific effector cells
  –Early (4-96 hours)
  –Late (>96 hours)


DEFENSE MECHANISMS OF THE HUMAN HOST
•Innate Mechanisms (Innate immunity)
  –First line of defense
  –Non-specific
•Adaptive Mechanisms (Adaptive immunity)
  –Second line of defense
  –Highly specific with memory
•Cooperation between mechanisms


Innate Immunity
•Nonspecific host defenses that exist prior to exposure to an antigen. Involves the following components:
  –Anatomic
  –Physiologic
  –Phagocytic
  –Inflammatory
•Anatomic
  –Skin
  –Mucous membranes
•Physiologic
  –Temperature
  –pH
  –Chemical mediators


Role of skin

•Dead skin cells are constantly sloughed off, making it hard for invading bacteria to colonize.

•Sweat and oils contain anti-microbial chemicals, including some antibiotics.

Role of mucus and cilia
•Mucus contains lysozymes, enzymes that destroy bacterial cell walls.
•The normal flow of mucus washes bacteria and viruses off of mucus membranes.
•Cilia in the respiratory tract move mucus out of the lungs to keep bacteria and viruses out.

Role of phagocytes
•Phagocytes are several types of white blood cells (including macrophages and neutrophils) that seek and destroy invaders. Some also destroy damaged body cells.
•Phagocytes are attracted by an inflammatory response of damaged cells.
                            
Role of inflammation
•Inflammation is signaled by mast cells, which release histamine.
•Histamine causes fluids to collect around an injury to dilute toxins. This causes swelling.
•The temperature of the tissues may rise, which can kill temperature-sensitive microbes.


Role of fever
•Fever is a defense mechanism that can destroy many types of microbes.
•Fever also helps fight viral infections by increasing interferon production.
•While high fevers can be dangerous, some doctors recommend letting low fevers run their course without taking aspirin or ibuprofen.

Innate immune response
•Mediated (initiated) by phagocytes, NK cells and soluble proteins
•Phagocytes
  –Cells specialized in the process of phagocytosis(Capture, engulfment and breakdown of bacterial pathogen)
Macrophages
  Reside in tissues and recruit neutrophils
Neutrophils
  -Enter infected tissues in large numbers
  –Recognize common molecules of bacterial cell   surface using a few surface receptors
Physiologic Mediators of Innate Immunity
•Chemical mediators
  –Enzymes
  –Interferon
  –Complement
  •Three pathways
  –Classical
  –MB Lectin
  –Alternative


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Topic 1: Types of immunity continuation- Complement system)

Complement system
•Complement system represents a group of about 30 proteins which augment or complement the immune response.
•Most of these proteins are found in serum or on cell surfaces.
•Synthesized in liver as inactive precursors and are activated by proteolysis during their interaction in a sequential manner.
•Also produced by blood monocytes, tissue macrophages and epithelial cells of he gastrointestinal and genitourinary tract.

General properties

•Present in serum of all animals but its concentration is maximum in serum of guinea pig.
•Complement of one species are able to react with antibodies of other species but not to the same extent.
•C- proteins constitute about 5% of normal serum protein
•Are glycoproteins.
• Are synthesized rapidly in inflammatory responses – hence are called acute phase proteins.
•Heat labile and lost activity at 56⁰ C for 30 mins and inactivated. Immunoglobulins are not inactivated at this temperature.
•Binds with Fc potion of immunoglobulns .

Three main effects of complement are:

1. Lysis of cells (bacteria, allografts, tumor cells)

2. Generation of mediators of inflammation

3. Opsonization – enhancement of phagocytosis

•Complement components-

  - Components are designated by numbers (E.g. ; C1 –   C9) or latters (E.g. : Factor D)

  - (in serum inactive, activated sequentially as a   cascade)

•Complement receptors (cell surface, recognize activated components)
•Regulatory proteins of complement (both in serum and cell surface, inhibit activated components)
•Complement proteins: are proenzymes - activation by cleavage
•Example: 
                                                        C4
•                                                 ⁄                   

                                         C4a                        C4b

•          a = smaller fragment                                   b= larger fragment.

  .                -Diffusion                                                   -remains bound to microbe

•C-activation: alteration of C proteins such that they interact with the next component
•C-fixation: utilization of C by Ag-Ab complexes
•C-inactivation: denaturation (usually by heat) of an early C-component resulting in loss of hemolytic activity
•Convertase/esterase: altered C-protein which acts as a proteolytic enzyme for another C-component

Three pathway of complement activation

1.Classical pathway:-

Is antibody dependent pathway and triggered by formation of soluble antigen-antibody complex or by binding of the antibody to the antigen present on the target cell surface.

2.Alternative pathway:-

Is antibody independent pathway stimulated by antigen directly e.g. Bacterial cell surface components.

3.Lectin Pathway:-

Also antibody independent but resembles classical pathway.

Stages of complement Activation
Three main stages in the activation of complement by any pathway are
–Formation of C3 convertage
–Formation C5 convertage
–Formation of membrane attack complec(MAC)
•The initiation and formation of C3 convertage are different in classical and alternative pathway . These then follow the parralel route to merge at C5 convertage stage and finally generate the MAC by a common route.
 
•Sequential activation of complement components occurs via one of three pathways:
–the classic pathway,
–the lectin pathway, and
–the alternative pathway .
•Of these pathways, the lectin and the alternative pathways are more important the first time we are infected by a microorganism because the antibody required to trigger the classic pathway is not present.
•The lectin pathway and the alternative pathway are, therefore, participants in the innate arm of the immune system.
•All three pathways lead to the production of C3b, the central molecule of the complement cascade.
•The presence of C3b on the surface of a microbe marks it as foreign and targets it for destruction. C3b has two important functions:

  (1) It combines with other complement components to generate C5 convertase, the enzyme that leads to the production of the membrane attack complex and

  (2) it opsonizes bacteria because phagocytes have receptors for C3b on their surface.

Classical pathway
•part of acquired immunity.
•In the classic pathway, antigen–antibody complexes activate C1 to form a protease, which cleaves C2 and C4 to form a C4bC2a complex, C2a and C4b split off.
•The C4bC2a is C3 convertase, which cleaves C3 molecules into two fragments, C3a and C3b.
•C3b forms a complex with C4b,2b, producing a new enzyme, C5 convertase (C4b2a3b), which cleaves C5 to form C5a and C5b
•C5b binds to C6 and C7 to form a complex that interacts with C8 and C9 to produce the membrane attack complex (C5b,6,7,8,9), which causes cytolysis.
•Note that the "b" fragment continues in the main pathway, whereas the "a" fragment is split off and has other activities except C2a which binds and C2b which
•Only IgM and IgG fix complement.
•One molecule of IgM can activate complement; however, activation by IgG requires two cross-linked IgG molecules.
•Of the IgGs, only IgG1, IgG2, and IgG3 subclasses fix complement; IgG4 does not.
•C1 is bound to a site located in the Fc region of the heavy chain.
•C1 is composed of three proteins, C1q, C1r, and C1s.
•C1q is an aggregate of 18 polypeptides that binds to the Fc portion of IgG and IgM.
•It is multivalent and can cross-link several immunoglobulin molecules.
•C1s is a proenzyme that is cleaved to form an active protease.


Alternative pathway
•independnt pathway.
•In the alternative pathway, many unrelated cell surface substances, e.g., bacterial lipopolysaccharides (endotoxin), fungal cell walls, and viral envelopes, can initiate the process by binding C3 and factor B.
•This complex is cleaved by a protease, factor D, to produce C3bBb.
•This acts as a C3 convertase to generate more C3b.
•Alternative pathways are more important the first Time we are infected by a microorganism because the antibody required to trigger the classic pathway is not

• Usually activated by products of micro-organisms like endotoxin

• Other activators include:

  1. Complexes containing IgA

  2. Some virus-infected cells (e.g. EBV)

  3. Many gram negative and gram positive  organisms

  4. Parasites – Trypanosomes, Leishmania

  5. Erythrocytes

  6. Carbohydrates (agarose)

Lectin Pathway

•Also known as the MBL Pathway
• In the lectin pathway, mannan-binding lectin (MBL) also known as mannose-binding protein) binds to the surface of microbes bearing mannan (a polymer of the sugar, mannose).
•Binding causes activation of MASP (MBP- associated serine proteases)
•cleave C2 and C4 and activate the classic pathway.
•Note that this process bypasses the antibody-requiring step and so is protective early in infection before antibody is formed.

•complement system has four major function, including;
–lysis of infectious organisms,
–activation of inflammation, 
–opsonization and
–immune clearance

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Topic 1: Types of immunity continuation - Specific defenses/ adaptive

•Specific defenses are those that give us immunity to certain diseases.
•In specific defenses, the immune system forms a chemical “memory” of the invading microbe. If the microbe is encountered again, the body reacts so quickly that few or no symptoms are felt.

Adaptive immunity: mechanisms

•Cell-mediated immune response (CMIR)

  –T-lymphocytes

  –eliminate intracellular microbes that survive within   phagocytes or other infected cells

•Humoral immune response (HIR)

  –B-lymphocytes

  –mediated by antibodies

  –eliminate extra-cellular microbes and their toxins

•The major players in the immune system include:
–Macrophage
–T cells (helper, cytotoxic, memory)
–B cells (plasma, memory)
–Antibodies
 

•Antibody: a protein produced by the human immune system to tag and destroy invasive microbes.
•Antibiotic: various chemicals produced by certain soil microbes that are toxic to many bacteria. Some we use as medicines.
•Antigen: any protein that our immune system uses to recognize “self” vs. “not self.”


Antibody

•Antibodies are assembled out of protein chains.
•There are many different chains that the immune system assembles in different ways to make different antibodies.
•Antibodies can attach to B cells, and serve to recognize foreign antigens.

•Free antibodies can bind to antigens, which “tags” the antigen for the immune system to attack and destroy.


Antigen recognition
•Cells of the immune system are “trained” to recognize “self” proteins vs. “not self” proteins.
•If an antigen (“not self”) protein is encountered by a macrophage, it will bring the protein to a helper T-cell for identification.
• If the helper T-cell recognizes the protein as “not self,” it will launch an immune response.
•Cells of the immune system are “trained” to recognize “self” proteins vs. “not self” proteins.
•If an antigen (“not self”) protein is encountered by a macrophage, it will bring the protein to a helper T-cell for identification.
• If the helper T-cell recognizes the protein as “not self,” it will launch an immune response.

Helper T cells
•Helper T-cells have receptors for recognizing antigens. If they are presented with an antigen, they release cytokines to stimulate B-cell division.
•The helper T-cell is the key cell to signal an immune response. If helper T-cells are disabled, as they are in people with AIDS, the immune system will not respond.
B cells
•B-cells in general produce antibodies. Those with antibodies that bind with the invader’s antigen are stimulated to reproduce rapidly.
•B-cells differentiate into either plasma cells or memory B-cells. Plasma cells rapidly produce antibodies. Memory cells retain the “memory” of the invader and remain ready to divide rapidly if an invasion occurs again.
Clonal Selection

Role of antibodies
•Antibodies released into the blood stream will bind to the antigens that they are specific for.
•Antibodies may disable some microbes, or cause them to stick together (agglutinate). They “tag” microbes so that the microbes are quickly recognized by various white blood cells.

“Killer” T cells (natural killer cells)
•While B-cells divide and differentiate, so do T-cells.
•Some T-cells become cytotoxic, or “killer” T-cells. These T-cells seek out and destroy any antigens in the system, and destroy microbes “tagged” by antibodies.
•Some cytotoxic T-cells can recognize and destroy cancer cells.
  


Calling a halt
•When the invader is destroyed, the helper T-cell calls a halt to the immune response.
•Memory T-cells are formed, which can quickly divide and produce cytotoxic T-cells to quickly fight off the invader if it is encountered again in the future.

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Topic 1: Summary

Immunology is the study of the immune system and is a very important branch of the medical and biological sciences. The immune system protects us from infection through various lines of defence. If the immune system is not functioning as it should, it can result in disease, such as autoimmunity, allergy and cancer.

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Topic 2: Objectives

At the end of this topic, the learner shall be able to:

  1. Explain the interaction between nutrition and other careers
  2. Outline the different career opportunities of a nutritionist and dietitian
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Topic 1: Further Reading

1.Chematai, A.(2012).Immunology (3rd ed.), Nairobi: Jomo Kenyatta Foundation
2.Arora D. and BrijBala, A. (2011), Microbiology for Nursing and allied sciences, (2nd ed.), India: BS Publishers and Distributors PVT Ltd.
3.Gupte, S (2011). The short Textbook of Microbiology for Nurses, 2nd edition, New Delhi: Jay Pee Brothers.
4.Waugh, A., & Allison, G. (2014). Ross and Wilson Anatomy and Physiology in Health and Illness. Philadelphia: Elsevier.
DOWNLOAD ALL OF THESE BOOKS FROM THIS PORTAL, CHECK THE LEFT OPTION BAR AND CLICK DOWNLOAD ALL BOOKS, USE THE SUBSCRIPTION PORTAL AND ENROLL AND DOWNLOAD UNLIMITED LIBRARY OF BOOKS


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Topic 1: Skills And Competences In Nutrition And Dietetics

At the end of this unit, the learner should be able to:

  1. Explain the skills required in dietetics
  2. Explain the competencies required in nutrition and dietetics
Essential skills in dietetics

Dietitians need to possess a mature, confident and caring manner

Working with people and behavior change. When working one-on-one or in small groups you must be friendly and approachable in your correspondence. In addition it is important to understand and practice the theories of health promotion. For example, the Trans theoretical Model classifies people into five stages of change. By utilizing these theories when working with people you can best determine how to help them with their nutrition goals.

Computer skills (Basic IT skills). Nutrition jobs require work on a computer and often the Internet. You will be required to create spreadsheets, keep track of client information, use software to analyze the nutritional content of foods and develop meal plans, utilize email, get involved with web-based social media, and conduct informational research on the computer.

Organizational skills. These jobs are demanding. They require work outside the normal work day, and many involve several types of duties labeled under one position title. It may consultations with colleagues, research to conduct, papers to write among other responsibilities so time management and proper organization is key.

Research translation. Employment in the nutrition field often requires that you put complicated research findings and technical nutrition information into a form that can be understood by those not familiar with the field.

The ability to interact well with people from a wide range of backgrounds


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Topic 1: Skills And Competences In Nutrition And Dietetics [Cont'd]

Good interpersonal and communication skills are essential.

Critical Thinking- Using logic and reasoning to identify the strengths and weaknesses of alternative solutions, conclusions or approaches to problems.

Competences in nutrition and dietetics.

  1. Perform in accordance with the Code of Ethics for the Profession of Dietetics
  2. Refer clients/patients to other dietetics professionals or disciplines when a situation is beyond one's level or area of competence (perform)
  3. Participate in legislative and public policy processes as they affect food, food security, nutrition, and health care
  4. Supervise documentation of nutrition assessment and interventions
  5. Supervise counseling, education, and/or other interventions in health promotion/disease prevention for patient/clients needing medical nutrition therapy for uncomplicated instances of common conditions, e.g., hypertension, obesity, diabetes, and diverticular disease
  6. Supervise production of food that meets nutrition guidelines, cost parameters, and consumer acceptance
  7. Supervise nutrition assessment of individual patients/clients with uncomplicated instances of common medical conditions, e.g., hypertension, obesity, diabetes, and diverticular disease
  8. Coordinate and modify nutrition care activities among caregivers
  9. Conduct nutrition care component of interdisciplinary team conferences to discuss patient/client treatment and discharge planning


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Topic 3: Further Reading

1.      Martin Eastwood; Principles of Human Nutrition; second edition; Blackwell Publishing; 2010

2.      Introduction to Human Nutrition; 2nd Edition; Michael J. Gibney (Editor); Susan A. Lanham-New (Editor); Aedin Cassidy (Editor); Hester H. Vorster (Editor); March 2009; ; Wiley-Blackwell


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Topic 1: Standards And Ethics Of Professional Conduct

Objectives

By the end of this topic you should be able to;

  1. Discuss the standards in nutrition and dietetics
  2. Explain the ethics in nutrition and dietetics and disciplinary action against unethical behavior
  3. Explain the disciplinary action for unethical behavior in nutrition and dietetics
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Topic 1: Standards And Ethics Of Professional Conduct

Standards in Nutrition and Dietetics profession

Quality in practice

Competence and accountability

Provision of services

Application of research

Communication and application of knowledge

Utilization and management of resources

Ethics in nutrition and dietetics practice

International Code of Ethics

a)      Dietitians practice in a just and equitable manner to improve the nutrition of the world by:

§  Being competent, objective and honest in our actions

§  Respecting all people and their needs

§  Collaborating with others

§  Striving for positive nutrition outcomes for people

§  Doing no harm

§  Adhering to the standards of good practice in nutrition and dietetics

International Code of Good Practice

a)      Provision of Service and application of knowledge:

§  Provide high quality, cost efficient services in nutrition and dietetics

§  Provide services based on the expectation and needs of the community or client

§  Competently apply the knowledge of nutrition and dietetics and integrate this knowledge with other disciplines in health and social sciences

§  Work cooperatively with others to integrate nutrition and dietetics into overall care/service regardless of context

§  Work in partnership with clients and users of the service

b)     Developing practice and application of research

§  Interpret, apply, participate in or generate research to enhance practice

§  Develop a unique body of knowledge

§  Have an in-depth scientific knowledge of food and human nutrition

c)      Adopting an evidence-based approach to dietetic practice

§  Combine the evidence with the dietitian's expertise and judgment and the client’s or community’s unique values and circumstances to guide decision-making in dietetics

§  Apply an evidence-based approach to all areas of dietetic practice to improve health outcomes in individual clients, communities and populations

§  State the source of evidence underpinning practice recommendations and integrate knowledge of other disciplines

§  Reflect on how a dietitian’s own perspectives or biases may influence the interpretation of evidence

§  Ask questions, systematically find research evidence, and assess the validity, applicability and importance of that evidence

 

d)     Communication

§  Communicate effectively through nutrition education, education and training, development of policy and programs

§  Advocate for nutrition and dietetics, the alleviation of hunger and the value of services

§  Advance and promote the dietetics profession

e)      Quality in practice

§  Systematically evaluate the quality of practice and revise practice on the basis of this feedback

§  Strive to improve services and practice at all times

§  Maintain continued competence to practice

f)       Continued competence and professional accountability

§  Ensure accountability to the public

§  Accept responsibility for ensuring practice meets legislative requirements

§  Maintain continued competence by being responsible for lifelong learning and engaging in self-development



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Topic 1: Standards And Ethics Of Professional Conduct [Cont'd]

Disciplinary action for unethical behavior in nutrition and dietetics.

Kenya Nutritionist and dietitian institute (KNDI) is responsible for regulating the nutrition practice in Kenya. In cases of malpractice it is mandated to form a disciplinary committee.

a)      The Disciplinary Committee may order the removal from the register, suspension of registration or revocation of the practicing license of a practitioner or the imposition of a fine on a practitioner as may be prescribed by the Council, if that practitioner:

§  Has been convicted of an offence punishable by imprisonment, the commission of which in the opinion of the Institute has dishonored him in the public estimation

§  Has been guilty of negligence or malpractice in respect of his profession

§  Has been guilty of impropriety or misconduct, whether in respect of his profession or not.

b)      Upon an inquiry held by the committee, the person whose conduct is being inquired into shall be afforded an opportunity of being heard either in person or through an advocate.

c)      For the purposes of proceedings at any inquiry held by the disciplinary committee, the committee may administer oaths, and may subject to any regulation made under this Act, enforce attendance of persons as witnesses and the production of books and documents.

d)     Any person whose name has been removed from the register or whose license has been suspended shall forthwith surrender to the Institute his certificate of registration or license, and any person who fails to do so commits an offence.

e)      Any person aggrieved by the decision of the committee within 14 days from the date of the decision, appeal to the High Court.

 


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