Cell mediated immunity in the chinchilla (Chinchilla laniger): in vitro lymphocyte transformation

The cell mediated immune system of the chinchilla (Chinchilla laniger) was examined using both in vivo and in vitro methods. An in vitro lymphocyte transformation microassay was developed utilizing tritiated thymidine incorporation into spleen cells stimulated by the nonspecific mitogen, phytohemagglutinin-M. Peak stimulation of blastogenesis occurred between 48 and 72 hours of incubation with 5 X 10(6) cells/ml in 12.5 mul phytohemagglutinin-M/ml. In spleen cell cultures from chinchillas sensitized 2 weeks previously with Freund's complete adjuvant plus additional Mycobacterium tuberculosis, incubation of 2.5 X 10(6) or 5 X 10(6) cells/ml with 50 mug/ml of the specific antigen, purified protein derivative, produced marked blastogenesis after 96 hours. The blastogenic response of the chinchilla to this specific antigen was extraordinarily high when compared with transformation responses of canine, bovine and avian peripheral blood lymphocytes utilizing a similar microassay system. The macroscopic in vivo delayed cutaneous hypersensitivity response to an intradermal injection of 10 mug purified protein derivative into chinchillas previously sensitized with Freund's complete adjuvant plus Mycobacterium tuberculosis appeared to be deficient. Grossly, erythema and induration were very slight or absent; however, histologically a slight cutaneous inflammatory response of mixed but predominantly mononuclear leukocytes was observed. The chinchilla's unique ability to display an extraordinary in vitro lymphocyte transformation response and its apparent inability to mount a consistent observable delayed cutaneous hypersensitivity response makes it an excellent model for the further study of the relationship of these phenomena to the total concept of cell mediated immunity.