Expansion of T cells negative for CD28 expression in HIV infection. Relation to activation markers and cell adhesion molecules, and correlation with prognostic markers

CD28 is a transmembrane glycoprotein that provides T cells with an essential co-stimulatory signal during antigen presentation. Using flow cytometry, we document here an expansion of CD28(-) T cells in HIV infection. Whereas the percentage of CD4(+)CD28(+) T cells among total lymphocytes was decreased, a small increase of the percentage of CD4(+)CD28(-) T cells was observed. In the CD8(+) subset, there was a marked expansion of CD8(+)CD28(-) T cells. An increased percentage of CD8(+) T cells positive for HLA-DR was found in both CD28(+) and CD28(-) cells. Results were similar for CD38 expression. HIV infection was also distinguished by a shift from LFA-1(low)CD28(low) to LFA-1(high)CD28(high) and LFA-1(high)CD28(neg) expression pattern on CD8(+) T cells. Negative correlations were found between percentage and absolute number of CD8(+)CD28(+) T cells and several serum parameters usually associated with poor prognosis (IgA, IgE, beta 2-microglobulin and HIV-1 p24 antigen). Thus, HIV infection is characterized by a marked expansion of CD28(-) T cells with an abnormal expression of activation markers and cell adhesion molecules. In addition, CD8(+)CD28(+), but not CD8(+)CD28(-) or total CD8(+) T cell numbers, correlated with the levels of established serological markers of disease severity or progression and may, therefore, have predictive value.