Defect in ZAP70 Signaling

The ZAP-70 protein kinase has been reported to cause a unique immunodeficiency. This kinase is expressed on T cells and is associated with the CD3 Z chain of the TCR complex. TCR and ligand binding trigger the Src kinases that phosphorylate ITAMs on the Z chain. Tyrosine phosphorylation of proteins cannot occur in the presence of a defective ZAP-70. This results in a lack of mature CD8 cells in the peripheral blood and defective activation of CD4 cells (Fischer and Arnaiz-Villena, 1995).

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