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 glioblastoma s exhibit T cell anergy, In this report, we further investigate the na ture of this T cell anergy, The results demonstrate that tumor size bu t not location correlates with decreased mitogen or anti-CD3 mAb respo nsiveness of T cells obtained from patients, Stimulation of the TCR/CD 3 complex on these patients' T cells revealed defects in early transme mbrane signaling, Both PHA and anti-CD3 mAb activated PEL and T cells obtained from patients exhibited a marked decrease in the tyrosine pho sphorylation of a number of proteins, In particular, decreased phospho rylation of pp100 and phospholipase C gamma 1 (PLC gamma 1) was observ ed, In addition, PLC gamma 1 and p56(lck) protein levels were dramatic ally 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 o f free intracellular calcium concentrations ([Ca2+](i)) after mitogen (PHA) stimulation or ionomycin treatment of T cells obtained from pati ents revealed that they mobilize less calcium than do T cells obtained from normal subjects, Stimulation of T cells obtained from patients w ith PMA and ionomycin, which should bypass the requirement for PLC gam ma 1 activation as well as directly activate the p21(ras) signaling pa thway, did not restore the proliferative capacity of these T cells to normal levels, These results indicate that the anergy observed in T ce lls obtained from these patients is a consequence of one or more defec ts in the early transmembrane signaling events associated with TCR/CD3 stimulation.