The progency of C57BL/6 mice consisting of three groups: with signs of slow influenza infection ("dwarf"), "nude-like" resembling nude mice, and "nude-like" with spontaneous fur growth, was examined. The slow influenza infection in "dwarf" mice was found to be characterized by marked immunosuppression manifested by a sharp reduction of the number of antibody- and rosette-forming cells and blasttransformation of spleen lymphocytes into T- and B-mitogens. The most marked immuno-suppression was found in the "dwarfs" born to the females infected with the virus enriched with standard virions. "Nude-like" animals also had marked immunosuppression (particularly with regard to the rosette-formation), however, the "dwarfs" appeared to have more marked affection of B-cells as compared with "nude-like" mice. Gradual restoration of fur in a portion of "nude-like" animals (spontaneous growth) was due to sharp stimulation of immune responsiveness in them as manifested by a two-fold (as compared with the controls) increase in the number of antibody- and rosette-forming cells and normalization of spleen cell response to T- and B-mitogens. Differences between nude and "nude-like" mice consisting in the latter in the affection of not only T- but also B-link of immunity are discussed.