Complement mediated cell lysis of HIV-1 infected human cells measured as LDH release. Heat inactivated sera from HIV-v and NRP-v immunised mice were diluted 1/100 in PBS, combined with rabbit complement and added to cultures of T1 cells infected with HIV-1 field isolate UG-29-029 (clade A) or laboratory strain IIIB. The percentage of cell lysis was defined between the level of LDH release of non-infected T1 cells in the presence of complement without sera (0%) and the LDH released after lysing the same cells with Triton X-100 (100%). A positive response, indicated by an asterisk (*), was defined as an increment of lysis of at least 50% over that of HIV-1 infected cells in the presence of control (NRP-v) sera and with a statistical significance of p < 0.05. Represented are the averages of percentage cell lysis ± SEM.