Analysis of the T suppressor cell circuit which regulates contact sensitivity in mice infected with the virus of Newcastle disease.

The interaction between the virus of Newcastle disease (NDV) and the different cellular elements involved in the T suppressor cell circuit which regulates the expression phase of contact sensitivity has been investigated. NDV does not interfere with the production of the antigen-specific T suppressor factor (TsF) but inhibits its binding to T acceptor cells (Tacc). This cell when armed with TsF and exposed to the antigen corresponding to TsF releases a non-specific inhibitor of the transfer of contact sensitivity. More detailed analysis of the effect of NDV on the Tacc system showed that not only Tacc activity is impaired by NDV, but also the ability of antigen presenting cells (APC) to trigger Tacc armed with TsF is inhibited. The impairment of APC activity by NDV has been also investigated using another system, such as the induction of contact sensitivity by footpad cell transfer. The possibility that a virus-induced membrane modification might be responsible for the effect of NDV on the regulation of contact sensitivity is discussed.