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CD1
- nonclassical antigen presentation of nonprocessed, lipid based molecule to T cells
- loading occurs during various stages of endosomal trafficking
- can be self/foreign peptides
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CD3
- gamma, epsilon, delta, zeta
- expressed starting on DN T cells
- required for signal 1 of T cells
- analogous to T cell CD79 signal transduction
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CD4
- Class II MHC restricted T cells
- targeted by HIV
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CD8
Class 1 MHC restricted T cells
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VLA5, LFA1
- lymphocyte homing receptors to site of inflammation
- addressin molecules: VCAM1, ICAM1 (CD54)
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LFA1 (CD11, CD18)
- tight binding to ICAM-1 (CD54) for adhesion
- expressed on leukocytes
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CD54 (ICAM1)
- expressed on T cell and APCs
- binds to LFA (CD11, CD18)
- flu viruses also bind to nasopharynx ICAM1
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L-selectin
- target naive T cell to 2ndary lymphoid tissues
- binds to CD34 or GlyCAM1 on HEV or MAdCAM1 on mucosal endothelium
- initiates lymphocyte rolling and LFA activation
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MAdCAM1
- expressed on mucosal endothelium
- allows targeting of naive T cell by binding L-selectin
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CCR7
- chemokine receptor on naive T cells
- interacts with CCL21 on HEV to activate LFA1
- similar function as L-selectin, CXCR4
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CCL21
HEV surface molecule that interacts with CCR7 to upregulate LFA1 expression on lymphocytes so it can adhere tightly to ICAM and initiate diapedesis
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CD45RA, CD45RO
- naive T cells have CD45RA
- effector T cells have CD45RO--> lose L-selectin, gain more VLA4 --> bind to VCAM1 and ICAM1 on target tissue endothelium
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CCR9, alpha4:beta7 integrin homing receptor
- chemokine receptor on T cells that are activated in mucosal immune system
- allows permenant homing to mucosal immune system
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CLA
- expressed by skin homing T cells
- interacts with E-selectin on cutaneous endothelium
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CCL17
- cutaneous endothelial chemokine
- allows skin homing T cell targeting via CCR4 binding
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CCR4
- expressed on skin homing T cells
- interacts with CCL17 (endothelial chemokine)
- strengthens the CLA to E-selectin bond
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CCL27
- keratinocyte chemokine
- allows targeting of skin homing T cell via interaction with CCR10
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CCR10
- expressed on skin homing T cells
- binds to CCL27 on keratinocyte
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CD19, CD20, CD21
- B cell coreceptors that amplify BCR signal
- complexes with CD81 on APC and T cells
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CD22
- B cell surface molecule
- APC's CD32 binding downregulate B cell signal
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CD32 (FcγRII)
- expressed by macrophages, granulocytes, platelets
- inhibits B cell activation via BCR pathway
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CD25
- aka IL2 receptor
- autocrine growth signal released by T cell following signal 1 + 2
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CD40
- signal 2 for B cells
- also expressed on APCs
- binds CD4L (CD154) from T cells
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CD79αβ
- aka Igαβ
- expressed on mature B cells
- signal transduction by B cell antigen receptor complex
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CD80, CD86
- aka B7.1, B7.2
- B cell B7s costimulate T cells via CD28
- APC B7s inhibit activated T cells via CD152
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CD28
- expressed on most CD4 and CD8 T cells
- activated by B cell CD80/CD86 (B7.1, B7.2) signals
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CD152
- expressed on activated T cells
- binding to APC CD80 (B7.1/B7.2) inhibits T cell activity
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TLR4
activated by gram -ve bacteria LPS
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TLR2
activated by gram +ve bacteria lipoproteins, DAG
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PRRs
pattern recognition receptors: detects PAMPs
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PAMPs
pathogen associated molecular patterns: are expressed on microbes
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MBL
- mannose binding lectin
- an example of PRRs that recognize carbohydrates on microbes
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RIG1, MDA5
- PRRs in cytosol of most cells
- recognize viral dsRNA--> trigger IRF3, IRF7 transcription factor activation --> type 1 interferon production
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S1P1
- allows activated T cells to egress from thymus/LN to periphery
- S1P1 blockers suppress immunity
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TLR5
targets bacterial flagellin
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CCR5
expressed by Th1 for after activation
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CCR3
- expressed by Th2 cells after activation
- targets Th2 to GC so it can activate B cell isotype class switching
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