Footpad swelling responses to measure cell-mediated immunity. Footpad swelling responses in the BALB/c scid mice in the Latent Protocol (N = 9) and immunocompetent BALB/c recipients in the Latent (N = 7), Acute (N = 7), and Reactivation (N = 6) Protocols are shown. Included in the data sets are the footpad swelling responses of immune(N = 6) and nonimmune (N = 6) immunocompetent BALB/c mice. The BALB/c scid recipients of latent ganglia failed to develop a cell-mediated immune response, whereas four of the seven BALB/c wild-type recipients of latent ganglia showed a delayed-type hypersensitivity response. All of the immunocompetent BALB/c recipients of ganglia in the Acute and Reactivation Protocols exhibited cellular immune reactivity. Comparison of the footpad swelling response of the BALB/c immune mice, immunocompetent BALB/c recipients in the Reactivation Protocol and the Acute Protocol, and immunocompetent BALB/c recipients in the Latent Protocol with the BALB/c scid recipients in the Latent Protocol revealed that the response in the immunocompetent mice in each group was significantly greater than the response in the BALB/c scid mice (P < 0.001). Values are means ± SD.