Defective protein tyrosine phosphorylation and altered levels of p59fyn and p56ick in CD4 T cells from HIV-1 infected patients

Early in HIV infection, CD4⁺ lymphocytes exhibit the propertiesof an anergic state characterized by unresponslveness to mltogensor to TCR stimulation and by defective IL-2 production. As tyrosinephosphorylation is the earliest of the biochemical events initiatedby stimulation of CD3-TCR, we studied protein tyrosine phosphorylationin purified CD4⁺ lymphocytes from 25 asymptomatic seropositlvepatients (CD4 T cells >350/mm³) previously stimulated invitro by immobilized antl-CD3 mAb or by co-lmmoblllzed antl-CD3and antl-CD28 mAbs. Purified CD4⁺ lymphocytes from HIV-lnfectedpatients exhibited defective early protein tyrosine phosphorylationin response to CD3 activation when compared with normal subjects.This defect was observed mainly in patients in whom prollferatlveresponses to immobilized antl-CD3 ranged from 2 to 50% of controlvalues obtained in healthy donors, and was frequently associatedwith increased cellular levels of p59^fyn and decreased cellularlevels of p56^ick. Interestingly, these defects appeared to correlatewith the degree of impairment in thymidine incorporation. SinceCD28 mAbs have been reported to enhance prollferatlve responsesto the CD3–TCR pathway in cloned murine or human anergicmodels and to induce tyrosine phosphorylation in human T cells,we studied the role of CD28 mAb as a co-signal. Although antl-CD28co-stlmulatlon augmented the prollferatlve responses in bothcontrols and HIV-lnfected patients, It failed to correct thetyrosine phosphorylation pattern in the latter. Our resultssuggest a relationship between defective early protein tyrosinephosphorylation and impairment of proliferatlve responses inCD4 T cells from HIV-lnfected patients, and evidence is providedthat associated altered cellular levels of the fyn and Ick tyrosinekinases might play an important role in the anergic responseobserved early during HIV infection.