Immunity : The Immune system plays a role in combating infection, creating

inflammation (& consequently heart disease), controlling (or not) cancer and in auto-immune diseases.

Immune modulator molecules or cytokines and leukotrienes which are produced by the immune system can interact with most cells of the body

The immune system consists of organs, vessels, and cells that can be specific to a particular organism or “antigen” or non-specific. Some cells can identify foreign or damaged cells or microbes, others can kill in various ways.

Organs and cells of the Immune System

Organs of the immune system include the bone marrow where white blood cells are differentiated, the lymphoid organs (spleen, tonsils, appendix, lymph nodes) where lymphocytes live, and he lymphatic vessels where lymph is found.

Cells of the immune system include lymphocytes (many types), other white blood cells (neutrophils, basophils, and eosinophils), macrophages (found everywhere), and other dendritic cells.

Non-Specific immunity

White Blood cellsLymphocytes of the immune system in transit (20%)

Macrophages (the “eaters” of the immune system in transit) as monocytes (8%)

Neutrophils one of he best “eaters” of bacteria (70%) They leave blood vessels under signals from other immune system cells like macrophages

Other cells of the immune system such as basophils and eosinophils which has granules in their cytoplasm they can exocytose containing heparin and histamine (basophils) or toxic lysosome contents (eosinophils)

The lymphatic system is the

body’s surveillance

system .

It is made up of lymph nodes connected by

vessels that have lymph flowing in

them, and lymphoid organs.

The Lymphatic System

Lymph enters the vessels in the tissues all over the

body as more plasma

leaves arteries than enters veins.

Lymph vessels have

valves to prevent

backflow

In addition to lymph nodes there are other lymphoid tissues that

guard entry or transition such as tonsils or

appendix

The spleen filters blood through lymphocytic tissue and also through screening for red blood

cell damage or decay

Thymus is a gland that is

larger in children--- it matures T-

cells

Lymph nodes have entry and exit vessels and pathways where

the fluid flows through large numbers of

lymphocytes

Lymphocytes: cells of the specific immune systemSurveillance, intelligence, antibody

production and cytotoxic killers

• Three main types of lymphocytes are T-cells and B-cells.

• 10% are NK cells

• 15% are B-cells make antibodies

• 80% T-cells are cytotoxic killer cells, control of the immune response (suppressor T-cells), and the coordinators of the immune response (helper T-cells)

Lymphocytes are made in bone marrow from stem cells and matured either in bone marrow (B-cells) or in the

thymus (T-cells)

Membrane Proteins and LymphocytesAll cells make proteins called major histocompatitibity proteins (MHC) that pick up fragments of peptides and places them in the membrane.

This allows the immune system to recognize that the cell is(a) self and (b) normal, not infected, malignant or damaged.

Membrane Proteins and Lymphocytes

Some cells, such as macrophages, can eat bacteria or other microbes and break them up.

They make MHC Class II proteins which can “present” the antigen in the membrane for lymphocytes to “see” it.

Lymphocytes (1) Natural Killer cells

Lymphocytes (2) Antibody producing B-cells

B-cells have receptors (IgD) in their membranes where they can bind

antigens.

An antigen is a small fragment of a protein or lipoprotein from an organism or other invader (or from a cat saliva

protein)

The B-cell takes in the antigen and makes an MHC class II protein

containing the antigen that can then be “presented” to a helper T-cell which will

confirm that it is an invader or other undesirable

B-cell Activation to make antibodies, another view

Antibodies: what can they do?

Figure 14.13c

Figure 14.13e

Table 14.2

Figure 14.14

Lymphocytes (3) T-cells

• There are 2 main types of T-cells identified by membrane markers CD4 and CD8.

• All T-cells and B-cells make memory cells

• CD8 T-cells are killer T-cells and suppressor T-cells

• CD4 T-cells are Helper T-cells

CD8 T-cells

CD8 cells activation

CD4 T-cells

CD4 cell activation

Helper T-cells coordinate the immune response

Overview of the Immune Response

Fig. 22-25, p. 796

Response to infection

How Vaccines work

Exposure to a part of an organism, an attenuated organism or a tiny dose of live organism stimulates the immune system to form memory cells

Some response needs more than one exposure to get good coverage (examples are hepatitis B, human papilloma virus)

Fig. 22-22a, p. 794

Fig. 22-22b, p. 794

Fig. 22-26, p. 801

Mechanism of Allergy and Anaphylaxis