Adaptive Immune Responses

Vocabulary flashcards covering key concepts of innate and adaptive immunity, lymphocytes, antigen presentation, MHC, antibodies, and effector mechanisms based on the lecture notes.

Innate immunity

Non-specific first line of defense; immediate responses using physical barriers, chemical agents, inflammation, antimicrobial proteins, phagocytosis, and fever.

Adaptive immunity

Specific immune response; delayed; uses B and T lymphocytes; generates memory; includes humoral and cellular components.

Humoral immunity

Adaptive immunity involving B cells and antibodies circulating in body fluids.

Cellular immunity

Adaptive immunity mediated by T cells that respond to infected or abnormal cells.

Lymphocytes

White blood cells of the adaptive immune system; include B cells and T cells; originate in bone marrow or thymus.

B cells

Lymphocytes that mature in the bone marrow; differentiate into plasma cells and memory B cells; produce antibodies.

T cells

Lymphocytes that mature in the thymus; include helper T cells (CD4+) and cytotoxic T cells (CD8+).

Helper T cells (CD4+)

Coordinate immune responses; secrete cytokines; activate B cells and cytotoxic T cells; recognize antigen presented on MHC II by APCs.

Cytotoxic T cells (CD8+)

Directly kill infected or abnormal cells; recognize antigens presented on MHC I.

Antigen

Substance capable of inducing an immune response; typically proteins or polysaccharides that contain epitopes.

Epitope

Specific part of an antigen recognized by an immune receptor.

Antigen-presenting cells (APCs)

Cells that process and present antigens to T cells via MHC II (dendritic cells, macrophages, B cells).

MHC class I

Molecules on all nucleated cells presenting endogenous antigens to CD8+ T cells; signals infection or abnormality.

MHC class II

Molecules on APCs presenting exogenous antigens to CD4+ T cells; activates other immune cells.

Antigen processing

Breakdown of antigens into peptides for presentation on MHC molecules.

Antigen presentation

Display of peptide fragments on MHC molecules to T cells by APCs.

Clonal selection and expansion

Activation and proliferation of antigen-specific lymphocytes to form clones.

Immunological memory

Long-term memory from memory B and T cells enabling faster responses upon re-exposure.

Plasma cell

Effector B cell that secretes antibodies.

Memory B cell

Long-lived B cell that quickly responds to re-exposure with rapid antibody production.

Antibody (Immunoglobulin)

Y-shaped protein produced by plasma cells that binds specific antigens.

IgM

First antibody produced in a primary response; mainly in the bloodstream; promotes agglutination and activates complement.

IgG

Most abundant antibody in blood and tissues; crosses the placenta; neutralizes toxins and promotes opsonization.

IgA

Found in mucosal secretions (tears, saliva) and secretions; often a dimer with a secretory component; prevents pathogen adherence.

IgE

Antibody involved in allergic reactions and defense against parasites; binds to mast cells and basophils.

IgD

B cell receptor on the surface of naive B cells; role in B cell development and activation.

Neutralization

Antibodies block pathogens or toxins from binding to host cells.

Opsonization

Antibodies coat pathogens to enhance phagocytosis by macrophages and neutrophils.

Agglutination

Clumping of microbes due to antibodies binding to their surfaces.

Precipitation

Antibodies bind soluble antigens forming insoluble immune complexes that precipitate.

Complement activation

Antibody-antigen complexes activate the complement system, leading to lysis of pathogens.

Antigen processing and presentation (overview)

APCs process antigens and present peptide fragments on MHC molecules to T cells.

Co-stimulation

Second signal required for full T cell activation beyond TCR-MHC interaction.

Cytokines

Signaling proteins released by immune cells to regulate immune responses (e.g., ILs, IFNs, TNF).

Dendritic cells

Professional APCs that present antigens via MHC II to CD4+ T cells and initiate adaptive immunity.

Thymus

Primary lymphoid organ where T cells mature.

Bone marrow

Primary lymphoid organ where B cells mature.