Question

Suppose you have a mouse lacking Lck (Lck -/-). How might this affect TCR signaling?

Answer 1

lymphocyte-specific protein tyrosine kinase is an enzyme which is found in the specialized cell of immune system. It is a tyrosine kinase which phosphorylates tyrosine residue of certain protein that are involved in the cell signaling pathway of lymphocytes.

When the T cell receptor is engaged by the specific antigen presented by major histocompatibility complex , Lck acts to phosphorylate the intracellular chain of the CD3 and ζ-chains of the T cell receptor complex, allowing another cytoplasmic tyrosine kinase called ZAP-70 to bind to them. Lck then phosphorylates and activates ZAP-70, which in turn phosphorylates another molecule in the signaling cascade.

In the absence of Lck, phosphorylation of tyrosine residue will not take place.