[Combined immunodeficiency in LEC (Long Evans Cinnamon) rats with spontaneous hepatitis].

We investigated LEC rats immunopathologically which spontaneously developed hepatitis to find out the genesis, in comparison with non-hepatitis LEA (Long Evans Agouti) rats. 1) Wet weights of the spleen and thymus of 6-week old LEC rats were significantly lighter than those of LEA rats of the same age. 2) Serum IgG (Immunoglobulin G) in LEC rats remained markedly low after the age of two months and IgG antibody formation to SRBC (Sheep Red Blood Cell) as detected by plaque assay was also significantly suppressed. On the other hand, IgM antibody formation to SRBC was significantly suppressed through serum IgM level in LEC rats was normal or rather increased. 3) Blastogenic responses of spleen cells to PHA and Con A were much more suppressed in LEC rats than in LEA rats. 4) Cytostatic activity of intraperitoneal macrophages against tumor cells was more evident in LEC rats than in LEA rats, but there was no difference in NK (natural killer) activity between the two rat strains. From these results, it is speculated that spontaneously hepatitis-developing LEC rats possess T and B cell deficiency (combined immunodeficiency) and that the increase of macrophage and NK cell activities are linked to the genesis of developing hepatitis.