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Expressed on Class II MHC-restricted T cells (recognition of extracellular microbes).
Involved in thymocyte development, the development of helper T-cells and the primary receptor for HIV retrovirus. |
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Expressed by Class I MHC-restricted T-cells
Acts as an adhesion coreceptor in class I MHC-restricted T cell activation (development of CTLs) |
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Expressed on T cells
Part of the TCR complex critical for signal transduction resulting from TCR:MHC interaction (alpha and beta chains of TCR accomplish antigen recognition). |
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T-cell receptor that binds costimulator molecules B7-1 and 2 (CD80 and CD86) on APC (“co-stimulation”) and B-cells.
Interaction is critical for “priming” of naïve, mature, T-cells. |
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Expressed on antigen-stimulated CD4+ T cell
Binds CD40 on APCs (macrophages) and stimulates them to make more B7 and release IL-12 (make APCs “better APCs”).
Also activates B-cells at edge of follicular zone and endothelial cells |
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| Expressed on T-cells and binds to B7-1 and B7-2 molecules on APC for negative regulation of T-cells. |
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ADCC by NK cells
Fc receptor expressed by NK cells that binds to exposed Fc domains of IgG antibodies attached to cells (remember, NK cells also recognize cells lacking MHC presentation). |
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| Complement-2 (CR2) receptor expressed on B-cells to recognize C3d. CR2 activation serves as a “second” signal for activation of naïve B cells it the presence of an antigen. |
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Complement-1 Receptor (CR1) expressed on phagocytes and binds C3b opsonized microbes.
Also causes dissociation of C3 convertase subunits. |
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| Membrane cofactor protein (MCP) enables Factor1-mediated cleaveage of C3b and C4b for complement inactivation. |
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| blocks C9 binding and prevents MAC-formation. Important for complement innactivation |
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Definition
FC-gamma receptor expressed on macrophages and neutrophils.
It recognizes Fc domains of IgG1 and IgG3 antibodies that have opsonized target microbes. |
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| How are CD16 and CD64 related? |
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Definition
They are both Fc receptors that recognize IgG Fc domains.
CD16 is the receptor on NK cells important for ADCC of IgG-coated molecules
CD64 is the receptor on macrophages and neutrophils important for IgG1 and IgG3 opsonized microbes
C3b-opsonized microbes are recognized by CR1 or CD35 |
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| How are CD64 and CD35 related? |
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Definition
Both are receptors that recognize opsonized microbes.
CR1 (CD35) is expressed on macrophages and recognizes C3b-opsonized microbes
CD64 is an Fc receptor expressed on macrophages and neutrophils that recognizes IgG1 and IgG3-opsonized microbes |
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