Innate and Adaptive Immunity

• Immunity can be nonspecific (innate) or adaptive (specific).

Nonspecific (Innate) Immunity

• Involves general defenses against pathogens.
• Includes barriers, inflammation, and protective proteins.
• Lysosomes are antibacterial enzymes found in perspiration, saliva, and tears.
• The inflammatory response involves redness, swelling, heat, and pain.
• White blood cells are used to fight infection during inflammation.
• Protective proteins include the complement system, a group of proteins (e.g., C3) that aid immune response.

Adaptive (Specific) Immunity

• Targets specific pathogens.
• Involves B cells and T cells.
• Antigens are foreign molecules that trigger an immune response.
• Lymphocytes are white blood cells that recognize and attack specific pathogens.
• B cells are responsible for humoral immunity, which involves antibody production.
• T cells are involved in cell-mediated immunity, which is a direct attack on infected cells.
• Receptors are proteins on lymphocytes that bind specific antigens.

Clonal Selection Model

• B cells differentiate into plasma cells and memory B cells.
• Plasma cells produce antibodies.
• Memory B cells provide long-term immunity.
• Apoptosis is programmed cell death to remove unneeded or harmful cells.

Antibodies (Immunoglobulins, Ig)

• Y-shaped proteins that can be monomers, dimers, or pentamers.
• IgA blocks pathogen attachment in digestive and respiratory tracts.
• IgD signals B cell activation.
• IgE protects against parasitic worms and is involved in allergic reactions.
• IgG is the most abundant antibody, enhancing phagocytosis and activating complement.
• IgM is the first antibody produced, activating complement and agglutinating cells.
• Monoclonal antibodies are lab-made antibodies used in disease diagnosis.

Cell-Mediated Immunity (T Cells)

• The T cell receptor (TCR) binds to antigens presented by cells.
• An antigen-presenting cell (APC) displays antigens for recognition.
• Major Histocompatibility Complex (MHC) proteins present antigens.
• Cytotoxic T cells destroy virus-infected and cancer cells.
• Helper T cells activate B cells and other immune cells.

Immunity Types

• Active immunity is when the body produces its own antibodies (e.g., vaccines, infections).
• Passive immunity is when antibodies are received from another source (e.g., breast milk, injections).

Cytokines

• Produced by immune cells to regulate immune response.
• Interleukins are a type of cytokine that promotes cell communication.