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

Abstract

  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^lowCD28^low to LFA-1^highCD28^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, β2-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.