Subpopulation of peripheral blood lymphocytes in human encephalitis caused by group B arboviruses (Dengue, West Nile and Japanese B encephalitis.

Sera from twenty patients with clinically diagnosed viral encephalitis were studied during the acute and convalescent phases of illness for evidence of group B arboviral infection by demonstrating a rise in the titre of haemagglutination inhibiting (HI) antibodies. The immune status of these individuals was studied by quantitating peripheral T, T and 'null' lymphocytes. The percentage of total T cells in arboviral encephalitic (AE) group decreased significantly while that of B cells and 'active' T cells remained unaltered when compared to that of normal individuals. The null cell percentage, on the other hand increased significantly in the AE group. The absolute number of circulating T and B cells did not alter in the AE group while that of null cells rose significantly. The percentage and concentration of T. B and null cells during the convalescent phase of AE did not differ significantly when compared to those of the acute phase.