Immune System

Interferons

Proteins that help protect cells against viral infections.

Cytotoxic T cells

T cells that kill infected or abnormal cells.

NK cells (Natural Killer cells)

Cells that kill infected or abnormal cells without antigen specificity.

Respiratory Burst

Process where phagocytes release reactive oxygen species to destroy pathogens.

Membrane Attack Complex (MAC)

Complex formed by complement proteins to lyse bacterial cells.

Innate Immunity

Non-specific, immediate immune response involving barriers and phagocytes.

Adaptive Immunity

Specific immune response that involves memory T cells and B cells.

Humoral Immunity

Immune response mediated by B cells producing antibodies against extracellular pathogens.

Cellular Immunity

Immune response where T cells directly attack infected or abnormal cells.

Plasma Cells

Effector B cells that produce large amounts of antibodies.

Helper T Cells (CD4⁺)

Cells that activate B cells, cytotoxic T cells, and macrophages via cytokines.

Cytotoxic T Cells (CD8⁺)

T cells that kill infected cells using perforins and granzymes.

Regulatory T Cells (CD4⁺)

T cells that suppress immune responses and prevent autoimmunity.

Memory T Cells

T cells that provide rapid response to future infections.

Antigen-Presenting Cells (APCs)

Cells that present antigens to activate T cells, includes dendritic cells, macrophages, and B cells.

Major Histocompatibility Complex (MHC)

Molecules on cell surfaces that present antigens to T cells.

MHC I

MHC class present on all nucleated cells, recognized by cytotoxic T cells.

MHC II

MHC class present on APCs, recognized by helper T cells.

Antigens

Substances that provoke an immune response.

Haptens

Small molecules that become antigenic when attached to a protein.

Antibodies (Immunoglobulins)

Y-shaped proteins produced by plasma cells that neutralize pathogens.

Complement System

System that enhances immune responses by promoting inflammation, opsonization, and cell lysis.

Cytokines

Proteins that regulate immune responses and inflammation.

Perforins & Granzymes

Molecules released by cytotoxic T cells to induce apoptosis in target cells.

Chemotaxis

Process guiding immune cells to the site of infection.

Diapedesis

Process of immune cells exiting blood vessels to reach tissues.

Allergies

Hypersensitivity reactions of the immune system.

Fever

A body response that helps inhibit pathogen growth.

Positive Selection (T Cell Maturation)

Ensures T cells recognize MHC; non-recognizing cells die by apoptosis.

Negative Selection (T Cell Maturation)

Eliminates overly self-reactive T cells; prevents autoimmunity.