13.2 Immune receptor family

Immune receptors are made up of immunoglobulin superfamily which are involved in ligands recognition and contain tyrosine motif in their cytoplasmic tails. The cytoplasmic tail contains the immunoreceptor tyrosine-based activating motifs (ITAM) which are involved in the activation process. Phosphorylation of ITAM recruits the Syk/ZAP-70 tyrosine kinase which activates the immune cells. Contrary to ITAM some immune receptor contains immunoreceptor tyrosine-based inhibitory motifs (ITIM) which lead to inhibition of immune signaling. Immune receptors family includes B and T cell receptors, IgE receptor on mast cells, and activating and inhibitory receptor Fc receptors.

13.3 Characteristics of antigen receptor signaling

Signaling event in the T and B cells undergoes similar downstream pathway.

Binding of ligands to the receptor activates the Src family kinase that phosphorylates the ITAM motif in the cytoplasmic tail of the receptor. The phosphorylated tyrosine in ITAM recruits the Syk tyrosine kinases which further activate the downstream signaling cascade.