Module 7: The Immune System

To protect the body from pathogens, toxins, and other harmful substances.

Innate immunity is the first line of defense, providing immediate, non-specific protection. Adaptive immunity is a slower, specific response involving lymphocytes. Examples: skin (innate), antibodies (adaptive).

Thymus, bone marrow, spleen, lymph nodes, tonsils

Central lymphoid organs, such as the thymus and bone marrow, are responsible for the production and maturation of immune cells.

Mature T cells are produced in the thymus.

Lymph nodes filter lymph fluid and facilitate interactions between immune cells and antigens.

Immune cells recognize antigens through specific receptors on their cell surface that bind to particular antigens.

Helper T cells activate other immune cells (like B cells and cytotoxic T cells). Cytotoxic T cells directly kill infected cells.

Macrophages phagocytose pathogens and present antigens to T cells, initiating an immune response.

Antigen presenting cells (APCs) process antigens and display them on their surface with MHC molecules, which are then recognized by T cells.

B cells are produced in the bone marrow.

B cells produce antibodies, which neutralize pathogens and tag them for destruction. They also act as antigen-presenting cells.

Memory cells are long-lived lymphocytes that provide immunological memory of past infections for a faster response upon re-exposure.

Antibodies bind to antigens, neutralizing them or marking them for destruction by other immune cells.

Passive immunity is acquired through the transfer of antibodies from another source, such as from mother to fetus or through antibody injections.

Humoral immunity involves the production of antibodies by B cells, which target extracellular pathogens.

The complement system enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells, promote inflammation, and attack the pathogen's cell membrane.