Phagocytes express cytokine receptors that are produced during immune responses. Redundancy and pleomorphism of cytokines are in fact a consequence of their homologous receptors.
Types
Immunoglobulin (Ig) superfamily
- They are ubiquitously present throughout several cells and tissues of the vertebrate body, and share structural homology with immunoglobulins (antibodies), cell-adhesion molecules, and even some cytokines.
- Examples: IL-1 receptor types.
Hemopoietic Growth Factor (type 1) family
- conserved motifs in their extracellular amino-acid domain.
- Example: IL-2 receptor belongs to this chain, whose γ-chain (common to several other cytokines) deficiency is directly responsible for X-linked form of Severe Combined Immunodeficiency (X-SCID).
Interferon (type 2) family, whose members are receptors for INF β and γ.
Tumour Necrosis Factor (TNF) (type 3) family
- cysteine-rich common extracellular binding domain
- several other non-cytokine ligands like CD40, CD27 and CD 30
Seven transmembrane helix family
- ubiquitous receptor type in animal kingdom
- G-protein coupled receptors (for hormones and neurotransmitters)
- chemokine receptors
- binding proteins for the HIV virus (CXCR4 and CCR5)
See
- interleukines