Immunobiological characteristics of germfree and specific pathogen-free cats

The postnatal development of immune functions was investigated in kittens kept germfree from birth to 60 days of age and in the same cats after their transition to pathogen-free status until a maximum age of 1 year. The mean serum gamma-globulin level of germfree kittens was 0.5 +/- 0.1% at 10 days of age and increased to 11.5% at 1 year of age. Immunoglobulins IgG, IgA, and IgM were not detected in the serum during the first day of life. On the tenth day, IgG was the only immunoglobulin detected in the serum (mean 44 mg/dl), and all three classes of immunoglobulins were demonstrated at 60 days of age. Thereafter, immunoglobulin levels gradually increased with age. The total leukocyte count was constant, and differential counts disclosed a greater percentage of lymphocytes than that of neutrophils. There was 1-day delay in attaining a maximal incorporation of concanavalin A into lymphocytes of SPF cats as compared with conventional cats. The lymphocyte stimulation index was at least threefold greater in SPF cats than that seen in conventional cats.