CD4 and CD8 subpopulation changes during high dose intravenous immunoglobulin treatment.

High doses of immunoglobulin, when given intravenously (IVIgG), influence lymphocyte subset numbers and function. T-lymphocytes may be subdivided into two functionally different groups, helper/inducer (CD4+) and suppressor/cytotoxic (CD8+). Considerable functional as well as phenotypic heterogeneity exists within the two major subsets. CD4+ cells have been further subdivided into helper/inducer and suppressor/inducer sets by the differential binding of two monoclonal antibodies 4B4 (CDw29) and 2H4 (CD45R). Similarly, the CD8+ subset may be subdivided into suppressor and cytotoxic populations by the differential binding of monoclonal antibodies which identify the C3bi receptor (CD11). During IVIgG treatment of patients with autoimmune thrombocytopenic purpura (ATP) the change in CD4/CD8, due to an absolute increase in CD8+ cells, has been shown to correlate with the response to treatment as determined by platelet increase. However, the total CD4+ and CD8- numbers may not reflect changes in their constituent subpopulations. To examine this possibility the CD4 and CD8 subpopulations were analysed in 15 ATP patients, during IVIgG treatment, using a double fluorescence technique. In 10 of these patients the in vitro response to pokeweed mitogen (PWM) and Staphylococcus aureus Cowan I (STA Cowan I) was determined. There was no correlation between the change in CD8+ subpopulations and response to treatment but there was a correlation between the CD4+ change and platelet increment. In addition there was a correlation between the 4B4/2H4 change and the in vitro response to PWM but no correlation with the response to STA Cowan I. These findings suggest that during IVIgG treatment the CD4+ 4B4+ helper/inducer population is influenced resulting in reduced T-dependent B-cell activation.