Immune Response Glossary

The specific, acquired defense system that develops after exposure to pathogens, involving B cells and T cells that target particular antigens and create immunological memory for future encounters.

A Y-shaped protein (immunoglobulin) produced by plasma cells that binds specifically to an antigen, neutralizing the pathogen or marking it for destruction by other immune cells.

A molecule, typically a protein or polysaccharide on a pathogen's surface, that the immune system recognizes as foreign and that triggers an immune response.

A condition in which the immune system mistakenly attacks the body's own healthy cells and tissues, resulting from a failure of self-tolerance mechanisms. Examples include Type 1 diabetes, multiple sclerosis, and lupus.

A lymphocyte that matures in the bone marrow and is responsible for humoral (antibody-mediated) immunity. When activated, B cells differentiate into antibody-secreting plasma cells and long-lived memory B cells.

A signaling protein released by immune cells (especially helper T cells) that regulates the immune response by activating, recruiting, or suppressing other immune cells.

The ability of the adaptive immune system to remember previously encountered pathogens through long-lived memory B and T cells, enabling faster and stronger secondary responses.

A nonspecific innate response to tissue damage or infection, characterized by redness, warmth, swelling, and pain caused by histamine-mediated vasodilation and increased vascular permeability.

The nonspecific, immediate defense system present from birth, including physical barriers (skin, mucous membranes), chemical defenses (stomach acid, lysozyme), and cellular responses (phagocytes, inflammation, natural killer cells).

Cell surface molecules that display protein fragments for immune surveillance. MHC class I (on all nucleated cells) presents intracellular antigens to cytotoxic T cells. MHC class II (on antigen-presenting cells) presents extracellular antigens to helper T cells.

An immune cell that engulfs and digests pathogens through phagocytosis. Major types include neutrophils (rapid first responders) and macrophages (longer-lived cells that also present antigens).

A short-lived, terminally differentiated B cell that produces large quantities of antibodies (up to 2,000 per second) during an active immune response.

A lymphocyte that matures in the thymus. Helper T cells (CD4+) coordinate immune responses via cytokines. Cytotoxic T cells (CD8+) directly kill infected host cells by recognizing antigens on MHC class I molecules.

The administration of harmless antigens (weakened, inactivated, or partial pathogens) to stimulate adaptive immunity and create memory cells without causing disease, providing protection against future infection.