Chapter 1: Elements of the Immune System and their Roles in Defense

Vocabulary flashcards covering key terms from the lecture notes on the immune system.

Barrier

Physical or chemical barriers (e.g., skin, mucosal surfaces) that prevent pathogen entry.

Defensins

Antimicrobial peptides that disrupt pathogen membranes.

Microbiome

Community of microorganisms living in and on the body that influences immunity.

Inflammation

A tissue response to injury or infection involving redness, heat, swelling, and pain; part of innate immunity.

Innate immunity

Immediate, non-specific defense against pathogens, not requiring prior exposure.

Adaptive immunity

Specific immune response involving lymphocytes (B and T cells) with memory.

Cytokines

Protein signals that regulate and modulate immune responses.

Leukocytes

White blood cells; include neutrophils, monocytes, lymphocytes, etc.

Hematopoiesis

Formation of all blood cells from hematopoietic stem cells in the bone marrow.

Hematopoietic stem cell (HSC)

Multipotent bone marrow cell that self-renews and gives rise to all blood cells.

Common Myeloid Progenitor (CMP)

Progenitor that differentiates into cells of the myeloid lineage.

Common Lymphoid Progenitor (CLP)

Progenitor that differentiates into B cells, T cells, NK cells, and ILCs.

Myeloid lineage

Blood cells derived from CMPs, including RBCs, platelets, neutrophils, monocytes, etc.

Lymphoid lineage

Blood cells derived from CLPs, including B cells, T cells, NK cells, ILCs.

Macrophage

Phagocytic innate cell that also produces cytokines and activates T cells.

Monocyte

Circulating precursor that differentiates into macrophages in tissues.

Neutrophil

Most abundant WBC; primary phagocyte and first responder to infection.

Eosinophil

Granulocyte involved in defense against parasites and in allergies.

Basophil

Granulocyte involved in allergic responses and histamine release.

Mast cell

Tissue-resident granulocyte releasing histamine during allergic responses.

Dendritic cell

Antigen-presenting cell that activates T cells in lymphoid organs.

B cell

Lymphocyte that can become a antibody-producing cell; bears BCR.

T cell

Lymphocyte with TCR; includes helper and cytotoxic subsets.

B cell receptor (BCR)

Membrane-bound antibody on B cells that recognizes antigen.

T cell receptor (TCR)

Membrane-bound receptor on T cells that recognizes peptide-MHC.

Antibody (Immunoglobulin)

Secreted antibody molecules that neutralize pathogens or mark them for attack.

Plasma cell

Differentiated B cell that secretes antibodies.

Epitope

Part of an antigen recognized by an antibody or TCR.

Antigen

Molecule capable of eliciting an immune response and binding immune receptors.

Neutralization

Antibody action that blocks pathogen/toxin activity.

Opsonization

Antibody tagging that enhances phagocytosis of the pathogen.

MHC I

Major histocompatibility complex class I; presents peptides to CD8 T cells, on most nucleated cells.

MHC II

Major histocompatibility complex class II; presents to CD4 T cells on APCs.

CD4

Co-receptor on helper T cells; recognizes MHC II.

CD8

Co-receptor on cytotoxic T cells; recognizes MHC I.

Helper T cell (TH)

CD4+ T cells that orchestrate immune responses via cytokines.

Cytotoxic T cell (TC)

CD8+ T cells that kill infected or abnormal cells.

TH1

TH subset promoting macrophage activation and cell-mediated immunity.

TH2

TH subset promoting eosinophil/basophil/mast cell responses against parasites.

TH17

TH subset promoting neutrophil responses and mucosal defense.

TFH

T follicular helper cells that assist B cells in germinal centers.

Treg

Regulatory T cells that dampen immune responses to maintain tolerance.

NK cell

Natural killer cell; innate lymphocyte that kills infected/cancerous cells.

Innate lymphoid cell (ILC)

Lymphocytes of the innate system that mirror TH subsets functionally.

Primary lymphoid organs

Bone marrow and thymus; sites of B/T cell development.

Secondary lymphoid organs

Lymph nodes, spleen, MALT; sites of antigen encounter and activation.

MALT

Mucosa-associated lymphoid tissue; mucosal immune structures.

GALT

Gut-associated lymphoid tissue; intestinal immune structures.

BALT

Bronchial-associated lymphoid tissue; airway immune structures.

Lymph node

Secondary lymphoid organ where lymphocytes meet antigens.

Spleen

Secondary lymphoid organ with white pulp (lymphoid tissue) and red pulp (RBC turnover).

Red pulp

Spleen region involved in filtering and destroying old RBCs.

White pulp

Spleen region rich in lymphocytes; site of immune activation.

Germinal center

Site in lymphoid tissue where B cells proliferate and are selected.

Follicular dendritic cell

Cell in lymphoid follicles that presents antigen to B cells in follicles.

M cells

Specialized intestinal epithelium cells that sample lumen antigens for immune display.

Wright-Giemsa stain

Stain used to differentiate and visualize blood cells in samples.

Antigen-presenting cells (APCs)

Cells (macrophages, dendritic cells, B cells) that present antigen to T cells.

Antigen presentation

Display of processed antigen peptides on MHC molecules to T cells.

Memory cells

Long-lived lymphocytes that respond more rapidly upon re-exposure.