Introduction to Immunology and the Immune System

Study Notes

Immunology is the study of a host's reactions to foreign substances.
The field of immunology is relatively new, despite centuries of attempts to prevent disease.
Louis Pasteur is considered the father of immunology. His accidental observations significantly advanced disease prevention.
An attenuated vaccine uses a weakened form of the pathogen to stimulate immunity.
The debate between humoral and cellular immunity significantly advanced the understanding of immunology.

Innate immunity is the body's natural, non-specific defense system.
Adaptive immunity is a specific, acquired immune response targeted to particular pathogens.

Leukocytes (white blood cells) are key players in the innate immune system.
Phagocytosis is the process by which certain leukocytes engulf and destroy pathogens. Neutrophils, monocytes, and macrophages are capable of phagocytosis.
Tissue cells also play a role in innate immunity.
Natural Killer (NK) cells differ from T lymphocytes in their mechanisms of action.

B cells produce antibodies.
T cells play a crucial role in cell-mediated immunity. This includes different types of T cells, for example Helper and Cytotoxic T cells.
Plasma cells are antibody-secreting B cells.
Memory cells are long-lived immune cells that provide long-term immunity.

Primary Lymphoid Organs:
- Bone marrow: Produces various immune cells.
- Thymus: Maturation of T lymphocytes.
Secondary Lymphoid Organs:
- Lymph nodes: Filter lymph, containing lymphocytes and macrophages. Structure includes primary and secondary follicles. A secondary follicle is a germinal center.
- Spleen: Filters blood, containing lymphocytes and macrophages. It contains a periarteriolar lymphoid sheath (PALS).
- Other secondary lymphoid organs include tonsils and Peyer's patches. These play an overall important role in immunity.