BLASTOGENIC RESPONSE OF LYMPHOCYTES FROM FOALS INFECTED WITH RHODOCOCCUS-EQUI

The blastogenic response of lymphocytes from 16 newborn foals naturall y infected with Rhodococcus equi was investigated, in order to evaluat e the relationship between R, equi infection and depressed host respon se. Naturally infected foals showed evidence of R. equi infection at 5 -6 weeks of age, as determined by clinical, haematological, bacteriolo gical and serological methods. The blastogenic response of lymphocytes against phytohaemagglutinin was significantly depressed (stimulation index <1.80; P < 0.01, P < 0.05) in R. equi-infected foals at 5-6 week s of age compared with those of control foals. Serum IgG concentration decreased rapidly after foals reached 1 week of age, and minimum leve ls of IgG were observed at 5-7 weeks of age in R. equi-infected foals. This study suggests that the onset of R. equi infection may be associ ated with the depressed immune function of naturally infected foals du ring the first 5-6 weeks after birth.