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 Cgamma1 (PLCgamma1) was observed. In addition, PLCgamma1 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 PLCgamma1 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.