T Cell Receptor-Mediated Signaling Is Defective in T Cells Obtained from Patients with Primary Intracranial Tumors

It has been well established that patients with malignant glioblastomas exhibit T cell anergy. In this report, we further investigate the nature of this T cell anergy. The results demonstrate that tumor size but not location correlates with decreased mitogen or anti-CD3 mAb responsiveness of T cells obtained from patients. Stimulation of the TCR/CD3 complex on these patients' T cells revealed defects in early transmembrane signaling. Both PHA and anti-CD3 mAb activated PBL and T cells obtained from patients exhibited a marked decrease in the tyrosine phosphorylation of a number of proteins. In particular, decreased phosphorylation of pp100 and phospholipase Cγ1 (PLCγ1) was observed. In addition, PLCγ1 and p56^lck protein levels were dramatically reduced in T cells obtained from patients harboring a glioma. In contrast, the protein levels of p59^fyn were normal or only slightly reduced in T cells obtained from patients with gliomas. Quantitation of free intracellular calcium concentrations ([Ca²⁺]_i) after mitogen (PHA) stimulation or ionomycin treatment of T cells obtained from patients revealed that they mobilize less calcium than do T cells obtained from normal subjects. Stimulation of T cells obtained from patients with PMA and ionomycin, which should bypass the requirement for PLCγ1 activation as well as directly activate the p21^ras signaling pathway, did not restore the proliferative capacity of these T cells to normal levels. These results indicate that the anergy observed in T cells obtained from these patients is a consequence of one or more defects in the early transmembrane signaling events associated with TCR/CD3 stimulation.