Cellular Immunity and Cytokine Regulation

These flashcards cover the key vocabulary and concepts of cellular immunity, T-cell development and subsets, professional antigen-presenting cells, and the classification and function of major cytokine families based on the lecture notes.

Professional Antigen Presenting Cells (APCs)

Cells including dendritic cells, macrophages, and B cells that are highly efficient at presenting antigens to T-lymphocytes.

Dendritic cells

The most efficient professional APCs, characterized by high levels of MHC II molecules and the ability to recognize pathogen-associated molecular patterns (PAMPs).

Macrophages

APCs that upregulate surface MHC II after phagocytosis and recognize PAMPs.

Thymocytes

Precursors to T-cells that originate in the bone marrow and migrate to the thymus for development and selection.

Helper T-cells ($CD4+$)

A subset of T-lymphocytes that produces cytokines to alert B-cells to make antibodies, stimulates hematopoiesis, and initiates delayed hypersensitivity.

Cytotoxic T-cells ($CD8+$)

T-cells that recognize antigens associated with MHC class I and kill target cells presenting those antigens, such as virally infected cells.

Regulatory T-cells ($CD25+, CD4+$)

A subset of T-cells that downregulates the immune response and plays a critical role in immunological tolerance.

Th1 helper T-cells

Helper T-cell subset that stimulates $CD8+$ T-cells and macrophages, steering the immune response toward cell-mediated immunity.

Th2 helper T-cells

Helper T-cell subset that stimulates antibody production, steering the immune response toward antibody-mediated immunity.

Th17 helper T-cells

A helper T-cell population involved in autoimmunity.

Double negative stage

An early phase of T-cell development in the thymus where thymocytes lack both $CD4$ and $CD8$ surface markers.

Double positive stage

A stage of T-cell development where thymocytes express both $CD4$ and $CD8$ markers and undergo selection.

$CD3/TCR$ complex

The antigen receptor complex responsible for antigen recognition, which triggers thymocytes to differentiate during maturation.

MHC-peptide complex

A molecule that binds peptide fragments from pathogens and displays them on the cell surface for recognition by TCRs.

Positive selection

The process in the thymus where thymocytes showing intermediate binding to self-MHC molecules are selected to survive, becoming single-positive cells.

Negative selection (Clonal deletion)

The process where thymocytes that bind strongly to self-antigens undergo apoptosis to prevent autoimmunity.

Central Tolerance

The developmental process of eliminating autoreactive T or B lymphocytes to ensure the immune system does not attack self-peptides.

Cytokines

Small soluble proteins that act as chemical messengers to orchestrate and regulate innate and adaptive immune responses.

Synergy

A characteristic of cytokines where different cytokines act together to produce a combined effect.

Pleiotropy

The phenomenon where a single cytokine has multiple different biological actions on various target cells.

Redundancy

A characteristic where different cytokines perform the same function.

Antagonism

When one cytokine counteracts or blocks the effect of another cytokine.

Cascade induction

The action of one cytokine inducing a target cell to produce one or more additional cytokines.

Cytokine Storm (Hypercytokinemia)

Hyperstimulation of the immune system leading to hypotension, fever, edema, organ dysfunction, and potentially death.

Autocrine stimulation

Cytokine signaling where the protein acts on the same cell that secreted it.

Paracrine stimulation

Cytokine signaling where the protein acts on nearby cells.

Tumor necrosis factors (TNFs)

Pro-inflammatory cytokines that act as principal mediators of the acute inflammatory response to gram-negative bacteria.

Interferons (IFNs)

Pro-inflammatory cytokines that interfere with immunogens and cell division in response to tumors and microbes.

Interleukins (ILs)

Pro-inflammatory cytokines involved in communication between leukocytes, accentuating growth and differentiation.

Chemokines

Pro-inflammatory chemoattractant cytokines that regulate the recruitment and movement of cells via chemotaxis.

Transforming growth factors (TGFs)

Anti-inflammatory cytokines that downregulate and control cell growth and differentiation.

Colony-stimulating factors (CSFs)

Cytokines that stimulate the process of hematopoiesis.

$$IL-1$$

Produced by macrophages and monocytes; induces the acute phase response and the production of other cytokines like $IL-6$.

$$IL-2$$

A cytokine produced by activated T-cells that induces the proliferation of T cells, NK cells, and antibody production in B cells.

$$IL-10$$

A cytokine with anti-inflammatory effects that downregulates the immune response and the synthesis of cytokines like $IL-2$ and TNF\text{\alpha}.

IFN\text{\gamma}

Produced by NK cells and Th1 cells; increases antigen presentation and MHC expression while downregulating Th2 activity.

David Vetter

Known as the 'bubble boy', he was severely immunocompromised due to a defect in his $IL-2$ receptor.