Purified CD4+ T cells from SHIP +/+ or SHIP−/− mice (A) and Dok+/+ or Dok−/− mice (B) were stimulated through CD4 as described. In three separate experiments SHIP, SHIP-2, Dok, and Dok-2 were immunoprecipitated, and precipitates were analyzed using phosphotyrosine-, SHIP-1, SHIP-2, Dok-1, or Dok-2-specific antibodies, with similar results. Ratios (phosphorylation/protein levels) were determined using NIH Image software.