Video Lecture: Cellular Immunity and T Cell Differentiation

Vocabulary flashcards covering key concepts in cell-mediated immunity, T cell activation, differentiation, and cytotoxic mechanisms as described in the lecture notes.

Cell-mediated immunity

Adaptive immune response mediated by T lymphocytes; protects against intracellular pathogens and tumor cells; involves CD4+ and CD8+ T cells.

T lymphocytes

Lymphocytes that mature in the thymus and mediate cell-mediated immunity; differentiate into helper (CD4+) and cytotoxic (CD8+) subsets.

CD4+ T cells (Helper T cells)

Coordinate immune responses by cytokine secretion; activate macrophages, B cells, and other T cells; differentiate into helper subsets.

CD8+ T cells (Cytotoxic T Lymphocytes)

Killer T cells that destroy infected or transformed cells via cytotoxic mechanisms and cytokine production.

Activation signals for T cells

Two-signal model: TCR recognition of antigen with MHC plus a co-stimulatory signal (e.g., CD28–B7) to fully activate.

TCR-CD3 complex

T cell receptor associated with CD3 that transmits activation signals when antigen is recognized.

ITAM (Immunoreceptor Tyrosine-based Activation Motif)

Motifs in CD3 that become phosphorylated to propagate T cell activation signaling.

NF-κB

Transcription factor activated after TCR signaling; upregulates genes involved in T cell activation and cytokine production.

NFAT

Nuclear factor of activated T cells; transcription factor driving cytokine gene expression (e.g., IL-2).

IL-2

Interleukin-2; growth factor promoting T cell proliferation after activation.

IL-1β

Pro-inflammatory cytokine produced by macrophages; promotes fever and acute phase responses.

IL-6

Pro-inflammatory cytokine; stimulates acute phase response and fever; influences T cell differentiation.

TNF-α

Tumor necrosis factor alpha; inflammatory cytokine with systemic effects including fever and acute-phase response.

Co-stimulatory molecules

Second signals required for T cell activation; example: CD28 on T cells binding B7 on APCs.

Antigen-presenting cells (APCs)

Cells that present peptide antigens via MHC to T cells and provide co-stimulation; include dendritic cells and macrophages.

Dendritic cells

Professional APCs that prime naive T cells and direct their differentiation.

Macrophages

Antigen-presenting cells; phagocytose pathogens and secrete cytokines that guide T cell differentiation.

IL-12

Cytokine produced by macrophages/dendritic cells that promotes Th1 differentiation and IFN-γ production.

CD4+ T helper cell subsets

CD4+ T cells differentiate into functionally distinct helper subsets (e.g., Th1, Th2) in response to cytokines.

Th1 differentiation

Th1 polarization driven by IL-12 (and IFN-γ) promoting cell-mediated immunity against intracellular pathogens.

Th2 differentiation

Th2 polarization driven by IL-4 promoting humoral immunity and antibody responses.

CD8+ cytotoxic T cell differentiation

CD4+ help and APC signals drive naive CD8+ T cells to differentiate into cytotoxic effector cells.

Perforin

Pore-forming protein released by CTLs to deliver granzymes into target cells.

Granzyme

Serine proteases delivered by CTLs that activate apoptosis in the target cell.

MHC class I presentation

Antigen presentation of endogenous peptides on MHC I to CD8+ T cells.

MHC class II presentation

Antigen presentation of exogenous peptides on MHC II to CD4+ T cells.

Memory T cells

Long-lived T cells developed after activation that confer faster responses upon re-exposure.

Acute phase reactants

Liver-produced proteins (e.g., CRP, fibrinogen) induced by IL-1, IL-6, TNF-α during inflammation.

Fever

Systemic increase in body temperature caused by pyrogenic cytokines such as IL-1β, IL-6, and TNF-α.

GM-CSF

Granulocyte-macrophage colony-stimulating factor; stimulates bone marrow production of myeloid cells.

M-CSF

Macrophage colony-stimulating factor; promotes monocyte/macrophage development and survival.

IL-7

Cytokine important for T cell development and maintenance of T cell populations.

CD4+ helper cells promote CD8+ differentiation

CD4+ T helper cells secrete cytokines and activate APCs to enhance CD8+ T cell differentiation and memory formation.

Cytotoxic mechanism of CD8+ T cells

Killing of target cells expressing antigen via perforin/granzyme pathway and Fas-FasL interactions.