In third and fourth pharyngeal pouch, thymus immune-system cells {T cell}| produce lymphokines from precursors. T cells can phagocytize foreign cells and viruses {cellular immunity, T cell}. Cytotoxic T cells absorb damaged cells.
cell surface
T cells have surface protein receptors. These glycoproteins can have alpha, beta, gamma, and delta subunits. Receptor genes for these proteins are similar to immunoglobulin genes. Immunoglobulin superfamily has similar constant, joining, diverse, and variable regions and similar promoters.
T cells {CD4+ T lymphocyte} {helper T cell} can have cell-surface CD4-protein receptors {co-receptor}, which assist T-cell receptors. Helper T cells have T-cell receptors.
process
Helper T cells start disease-organism killing. Helper T cells secrete lymphokines, such as interleukin, interferon, colony-stimulating factor, and tumor necrosis factor. Lymphokines activate cytotoxic T cells, signal B cells to make antibodies, attract macrophages and platelets with chemotactic factor, multiply helper T cells, and multiply immune precursor cells.
regulatory T cells
5% to 10% of helper T cells have CD25 surface protein and Foxp3 transcription factor and inhibit autoreactive CD4+ T lymphocytes.
problems
CD4+ T lymphocytes can alter to cause multiple sclerosis, insulin-dependent diabetes of youth, and rheumatoid arthritis.
Helper T cells {regulatory T cell} {CD4+CD25+ T cell} {T-reg cell} {T regulatory cell} can inhibit helper-T-cell immune responses, rather than secrete cytokines or engulf infected cells. 5% to 10% of CD4+ T lymphocytes are regulatory T cells.
receptors
Regulatory T cells have T-cell receptors, CD4-protein receptors, and CD25 surface proteins, which are in interleukin-2 receptors. Interleukin-2 excites regulatory T cells.
transcription
They have Foxp3 transcription-factor protein, which makes molecules that can disable autoreactive T cells.
Perhaps, antigen-specific receptors are stronger than the ones for autoreactive CD4+ T lymphocytes. Perhaps, regulatory T cells inhibit antigen-presenting cells from showing antigen. Perhaps, regulatory T cells cause antigen-presenting cells to release inhibitory cytokines. Perhaps, regulatory T cells inhibit autoreactive CD4+ T lymphocytes directly.
problems
Foxp3-gene mutation can cause immune dysregulation polyendocrinopathy enteropathy X-linked chromosome syndrome {IPEX syndrome} and autoreactive immune systems. Scurfy mice have autoreactive immune systems.
T cells {dendritic cell} can have surface molecules that bind to non-self proteins and attract T cells to breakdown protein. Then they usually die.
Cells {antigen-presenting cell} can contact T cells, to present protein fragments {supramolecular activation cluster, antigen} that they removed from viruses or bacteria, and so activate T cells. Supramolecular-activation clusters have outer rings for adhesion and central spots for recognition. Proteins move to form patterns, using cytoskeletons.
4-Zoology-Organ-Immune System-Cells
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Date Modified: 2022.0225