Beta2-microglobulin and other cell-surface glycoproteins {major histocompatibility protein}| (MHC) can be for cell recognition.
number
Humans can have 100,000 different surface-protein sets.
polymorphism
Cell-surface glycoproteins can be highly polymorphic.
genes
MHC genes are similar to genes for antibodies and T-cell receptors {immunoglobulin superfamily, MHC}. MHC genes do not vary through rearrangement. MHC Class I genes are expressed in all cells. MHC Class II genes make glycoproteins for B cells and macrophages. Other MHC genes make blood-complement proteins and other cell-surface proteins.
receptors
Cytotoxic T cells recognize glycoproteins.
metabolism
MHC Class I glycoproteins cut bacterial and viral antigens into peptides, which then bind to cleft in MHC Class II glycoproteins. Helper T cells recognize antigen/MHC Class II complexes. Complement proteins CD4 and CD8 bind MHC to receptors at constant antibody regions and signal T cells to activate.
T cells can have antigen receptors {T cell receptor} (TCR).
Cell-surface proteins can have classes {tissue typing}|.
Phagocyte-cell receptors {Toll-like receptor} (TLR) can recognize lipopeptides. TLR1 detects bacterial lipopeptides and parasite GPI-anchored proteins. TLR2 detects Gram-positive-bacteria cell-wall lipoteichoic acids. TLR3 detects virus double-stranded RNA. TLR4 detects Gram-negative bacteria by binding to lipopolysaccharide. TLR5 detects bacteria-flagella flagellin. TLR6 detects fungi zymosan. TLR7 detects virus single-stranded RNA. TLR8 detects virus single-stranded RNA. TLR9 detects bacterial and virus CpG sequences.
metabolism
Inside cells, TLRs make MyD88, Mal, Tram, and/or Trif. These make NF-kappaB, which enters cell nuclei to start cytokine production.
evolution
TLR are in plants and animals. Tobacco has N protein that detects tobacco mosaic virus. TLR probably started in one-celled organisms.
4-Zoology-Organ-Immune System-Protein
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Date Modified: 2022.0225