FIG. 7.

Cooperative enhancement of T-cell antigen receptor signaling by Clnk and HPK-1. Jurkat Tag cells were transfected in duplicate with the indicated cDNAs in the presence of an IL-2 promoter-luciferase reporter plasmid. After 40 h, cells were stimulated as described in Materials and Methods with either anti-CD3 MAb OKT3 (anti-CD3) or the combination of PMA and ionomycin (PMA+iono). (A) Luciferase assay. Luciferase activity is expressed as the percentages of values obtained in cells stimulated with PMA plus ionomycin. Assays were conducted in duplicate. The average value is shown. (B) Immunoblots. The expression levels of HPK-1 and Clnk were determined by immunoblotting of total cell lysates with the appropriate antisera (denoted by “α” designations). Exposures, 15 h.