The Immune System


There are physical, chemical, and cellular defenses against invasion by viruses, bacteria, and other agents of disease.

During the early stages of an infection, there is an inflammatory response

During later stages, leucocytes produce immune responses


Surface coverage - the first line of defense


Non-specific responses - the second line of defense

Macrophage destroying bacterial cells


The Immune System (Specific Responses) - the third line of defense

Types of cells involved in the immune system:

Each type of virus, bacteria, or other foreign body has molecular markers which make it unique

Thus, immunological specificity and memory involve three events:

(1) Recognition of a specific invader

(2) Repeated cell divisions that form huge lymphocyte populations

(3) Differentiation into subpopulations of effector and memory cells

Antigen-presenting cell - a macrophage which digests a foreign cell, but leaves the antigens intact. It then binds these antigens to MHC molecules on its cell membrane. The antigen-MHC complexes are noticed by certain lymphocytes (recognition) which promotes cell division (repeated cell divisions)

Molecular cues that stimulate lypmphocytes to create an immune response

T cells (Helper T cells and Cytotoxic T cells)

Cell-mediated immune response

B cells and Antibodies

Antibody-mediated immune response

Where do all of these interactions take place? - in the lymph nodes.