Chapter 17: Specific Immunity (Adaptive Immunity)

Vocabulary flashcards covering key concepts from Chapter 17 on specific (adaptive) immunity.

Specific immunity (adaptive immunity)

The targeted immune response to particular pathogens, mediated by T and B lymphocytes and memory.

Antigen

A foreign molecule or part of one that elicits an immune response.

Antibody (immunoglobulin)

A Y-shaped protein produced by B cells that binds specifically to an antigen.

Immunoglobulin

Another term for antibody.

Titer

The concentration of antibodies present in the blood at a given time.

Apoptosis

Programmed cell death used to eliminate infected or damaged cells.

Acquired immunity

Immunity developed after exposure to antigens, either naturally or artificially.

Natural acquired immunity

Immunity obtained through natural exposure, such as infection or maternal antibody transfer.

Artificial acquired immunity

Immunity obtained through medical intervention, such as vaccines or immunoglobulin therapy.

Passive acquisition

Receiving preformed antibodies from another source; the recipient doesn't produce antibodies.

Active acquisition

The host actively produces antibodies.

Passive natural

Colostrum (breast milk) and placental antibodies transferred to the infant.

Active natural

Illness/infection in which the immune system produces antibodies.

Passive artificial

Immunoglobulin injections delivering preformed antibodies.

Active artificial

Vaccination or immunization that prompts antibody production.

Killed (inactivated) vaccine

Vaccine containing killed pathogens; cannot cause infection but triggers immunity.

Attenuated vaccine

Vaccine with a weakened live pathogen; usually strong immunity but may be risky for immunocompromised.

Cell-mediated immunity

Immunity mediated by T cells; targets intracellular pathogens.

Humoral immunity

Immunity mediated by B cells and antibodies in body fluids; targets extracellular pathogens.

B cells

Lymphocytes that mature in bone marrow and differentiate into plasma cells to produce antibodies.

Bursa-derived (B) cells

Origin of B cells named after the Bursa of Fabricius; in humans they mature in the bone marrow.

Plasma cells

Differentiated B cells that secrete antibodies.

Immature B cell

B cell that has not yet been stimulated by an antigen.

Mature B cell

B cell that has encountered antigen and differentiates into a plasma cell.

IgG (Immunoglobulin G)

Monomer; most abundant antibody; crosses placenta; supports immune memory; half-life ~20 days.

IgM (Immunoglobulin M)

First antibody produced in primary responses; half-life ~10 days.

IgE (Immunoglobulin E)

Mediates allergic reactions; short half-life (~2 days).

IgA (Immunoglobulin A)

Dimer; predominant in mucosal immunity; half-life ~6 days.

IgD (Immunoglobulin D)

Monomer; B-cell receptor; mostly membrane-bound; half-life ~2 days.

Primary immune response

Initial exposure to an antigen; IgM appears first, followed by IgG; memory formed.

Secondary immune response

Re-exposure to the same antigen; rapid IgG production with higher titer; IgM often minimal.

Epitope (antigenic determinant)

The specific part of an antigen recognized by an antibody or T cell receptor.

Variable region (Fab)

Antigen-binding region of an antibody; highly diverse due to gene recombination; ~110–130 amino acids.

Constant region (Fc)

The constant region of an antibody; determines class and effector functions.

Antibody-antigen complex

Bound antibody and antigen; initiates immune effector mechanisms.

Agglutination/neutralization

Antibodies cross-link antigens causing clumping or neutralizing pathogen activity.

Opsonization

Antibodies coat an antigen to enhance phagocytosis.

Complement activation

Antibody binding triggers the complement cascade, promoting lysis or phagocytosis.

Antigen-presenting cell (APC)

Cell that displays antigen fragments on MHC to T cells (e.g., macrophages).

Major Histocompatibility Complex (MHC)

Surface molecules that present antigen fragments to T cells, signaling infection.

Interleukin-1 (IL-1)

Cytokine released by APCs that activates helper T cells.

Helper T cells (CD4+)

T lymphocytes that coordinate immune responses; express CD4.

Cytotoxic T cells (CD8+)

T lymphocytes that kill infected cells; express CD8.

Interleukin-2 (IL-2)

Cytokine that activates T cells and B cells.

Perforin

Exocytosed enzyme that creates pores in target cell membranes to induce death.

Memory cells

Long-lived lymphocytes that confer faster responses on re-exposure to the same antigen.

Antigen presenting cell changes in MHC

APCs alter MHC to signal that they contain a processed antigen.

Cytokine signaling in coordination of immunity

Interleukins and other cytokines coordinate activity between B and T cells and APCs.