Protein phosphatase that acts preferentially on tyrosine-phosphorylated MAPK1. Plays a role in the regulation of T and B-lymphocyte development and signal transduction. H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Inhibited in cells after FCER1A triggering. Monomer. Interacts with MAPK1, MAPK3 and several other MAP kinases. Expressed exclusively in thymus and spleen. Phosphorylated on serine residues in resting T-cells. Phosphorylation increases upon exposure to stimuli that increase intracellular cAMP levels. Phosphorylation leads to dissociation of bound MAP kinases. Oxidized at active site cysteine. Treatment with pervanadate (vanadate and H(2)O(2)) or with antigen enhanced oxidation of active site cysteine (By similarity). Belongs to the protein-tyrosine phosphatase family. Non-receptor class subfamily.