Biology 2404 A&P Basics

Immunity is the body’s ability to defend itself against pathogens which are disease causing organisms. The immune system has two major divisions: nonspecific or innate immunity and specific or acquired immunity.

Nonspecific or innate immunity forms the first two lines of body defenses.

1^st line defenses are barriers such as physical barriers, chemical secretions and mechanical processes.

They try to prevent entry, access, or attachment.

Physical barriers skin, mucous membranes, epithelial linings

Chemical secretions tears, saliva, mucus, stomach acid (HCl)

Mechanical processes coughing, sneezing, peristalsis, urination

Second Line Defenses

2^nd line nonspecific defenses are activated if the pathogen gets through 1^st line body defenses. Response involves the following:

Cellular WBCs phagocytosis or other means of destruction
Fever increases in body temperature by resetting the hypothalamic thermostat
Inflammation reaction of tissues to injury causing redness, swelling, pain, and heat
Proteins
* Interferon proteins secreted to help protect cells during viral infections.
* Complement proteins that cause increased phagocytosis, inflammation, and cell lysis or destruction.

Macrophages are the key white blood cells in tying the two immune divisions together by acting as an antigen presenting cell (APC). By phagocytizing any foreign substance in a second line defense mechanism, they also help to alert the 3^rd line body defenses of the specific or acquired immune response by encorporating foreign antigen into their HLA (self) membrane markers.

Blood cells

Neutrophils: Drawing, Histology 1 , Histology 2

Macrophage: Drawing, Histology

WBC Immune Cells:

Second Line defense cells

Third Line Body Defenses

Third line body defenses are activated when second line defenses are activated. The acquired or specific defenses have two subdivisions. Humoral mediated immunity is responsible for a fluid defense using antibodies. Cell mediated immunity is responsible for a tissue defense using cells.

A summary follows:

Humoral Immunity B-lymphocytes (B cells) Antibodies in fluid

Cell Mediated Immunity T-lymphocytes (T cells) cells in tissue

Blood cells

Lymphcytes : Drawing, Histology

Eosinophils: Drawing, Histology

Basophils: Drawing , Histology

Third line defense cells

Red Bone Marrow : specimen, histology

Antibody General Drawing

Specific Immune Blood Cells Drawing

The specific immune system is designed to respond to specific parts of foreign substances. Cells that are programmed for specific defenses must learn or acquire “knowledge” about normal and abnormal substances. These substances that may trigger an immune response are called antigens (Ag). The normal or self antigen markers are proteins located ON the cell membrane and most are termed MHC-HLA, which is the major histocompatability complex for the Human Leukocyte Antigen. Blood cells have their own self antigen markers called agglutinins and are labeled as the ABOD blood groups.

If a pathogen or body cell does not display the expected self antigens on their membrane, it will normally trigger phagocytosis by the macrophage and activation of the B and /or T lymphocytes. Most foreign antigens are proteins found on the surfaces of the invading pathogen, such as bacteria, virus, protozoa, fungus, and parasitic worms (helminthes).

In response to an invading pathogen with foreign (non-self) antigens, the immune cells will rely on chemicals to organize, signal, communicate, and coordinate an appropriate defense response. These chemicals collectively called cytokines enable a system wide response and control for the entire immune system.

Macrophages are the nonspecific WBC usually involved with aiding the specific immune response. By digesting foreign substances, macrophages also process the foreign antigen and show or present this antigen to T and / or B lymphocytes. These lymphocytes respond by dividing into subpopulations secreting more cytokines like interleukins to activate and recruit other WBCs.

EM picture of Macrophage attacking a bacterium

In response to a pathogen, the daughter cells of the T and B lymphocytes provide unique defense mechanisms. The daughter cells of some of the T-lymphocytes are called cytotoxic T cells. These cells when fully activated will kill the pathogen. Hence, their functional name is the killer T cell that form part of the CD8 population of T cells. Other T lymphocyte daughter cells are helper T cells. Their function is to help communicate and coordinate an appropriate response from all the WBCs. The T-helper cell belongs to the CD4 subpopulation of T cells. Another T lymphocyte daughter cell is the suppressor T cell. Their function is to help stop the immune system response once the pathogen has been eliminated. They belong to the CD8 subpopulation of T cells.

B lymphocytes can be activated by cytokines from macrophages, T lymphocytes, or by encountering free (non-digested) antigen. Their daughter cells, known as plasma cells, produce antibodies or Immunoglobulins (Ig). Immunoglobulins are large globular proteins in 4 linked chains that form a double “Y” shape.

Immunoglobulin Drawing

There are 5 classes of antibodies that make up the gamma (immuno-) globulins of plasma proteins. These are:

Immunoglobulin Gamma	IgG *	most predominant antibody	found throughout the body
Immunoglobulin alpha	IgA	found in secretions	respiratory and digestive
Immunoglobulin Mu	IgM *	First antibody that is secreted	forms the agglutinogens of blood
Immunoglobulin Epsilon	IgE	attaches to mast cells	seen associated with allergic reactions
Immunoglobulin Delta	IgD	receptor on B lymphocyte	for free (non-digested) antigen binding

* Can activate complement proteins.

Immunoglobulin Drawings

Ig G

Ig A

Ig M

Ig E

Ig D

Antibodies do not attach to kill foreign antigens, but rather mark the pathogen for destruction by some other means. Antibodies can function to neutralize toxic secretions of a pathogen, agglutinate large cell bound antigens, precipitate smaller soluble antigens, or activate complement which will cause increase phagocytosis by macrophages, cause more inflammation, and activate a membrane protein attack complex to cause cell lysis.

Antibodies can be identified on special, specific tests such as the IFA (immunoflourescence antibody test), antibody titers to determine levels of each of the gamma globulins, ELISA tests, and the Coombs test.

Antibody Titer Drawing:

First Exposure to Antigen

Second Exposure to Antigen

Elisa Test

The specific immunity can also be grouped as a response according to activation and how acquired.

Activation can be active or passive where active means the immune cells responded to initiate the defenses and passive means the defense cells or proteins were made by someone else’s immune system. The method of acquiring a specific response can be natural or artificial. Natural implies that it was made in a living organism; artificial implies that it was made in a laboratory.

The following combinations can be seen:

Natural Passive Immunity antibodies or cells were made in a living organism and passed on to another person. The recipient’s immune system did not make the antibodies or defense cells in response to a foreign antigen. Example: Antibodies passed from mother to baby in the milk

Natural Active Immunity antibodies or cells were made in a living organism and that individual’s immune system did respond to the foreign Ag. Example: Individual’s natural immune response to being infected by the common cold virus or any other naturally occurring disease.

Artificial Passive Immunity antibodies or cells were made in a laboratory. The person’s own immune system did not make this defense.Example: gamma globulin shots to treat rabies. This type of treatment is done when the disease would most likely kill the individual before an adequate immune response could be mounted.

Artificial Active Immunity antibodies or cells were made in a laboratory. The person’s own immune system responded to exposure of the foreign antigen. Example: vaccinations for polio, DPT, tetanus

Allergy Injection

Medical Terminology

Auto- self helminth- worm

Pent- five platy- flat

Py, pyo pus -septic putrid

Uni- one cid(e) kill

Febr- fever nos- disease

Vacc- cow zoo- animal

Immun/o- immune thym/o- thymus

Exercises/Activities

I. Blood cell ID part A,

Blood Cell ID part B

II. Lymphocyte Functions

III. Histology ID: Slide One, Slide Two, Slide Three

IV. Bone marrow : specimen, slide

V. Skin model

VI. Humoral Immunity

VII. AB titer report

Concept Map: Make a concept map of the immune system (cells, location, and function).
Include this map in your LAR lab report (if selected) as a document insert or as an additional PDF document scan.

Case Study

Rent the movie, "Osmosis Jones", from Warner Bros. Pictures starring Bill Murray and Chris Rock (rated PG). Watch and see how many organ systems are mentioned. List five of these systems and explain how the Immune System is involved in their particular protection and defense (in real life, not what the movie shows). Send this list and explanation to your instructor via email attachment for 5 extra points on the lymphatic/immune lab quiz.

Applications

AIDS

Allergies

Autoimmune diseases: MG, MD, MS, RA, SLE

Vaccines

Complement Fixation test

AB titer

IFA

ELISA

Interferon

Athymic atrophy (bubble boy)

Career: