EVALUATION OF CANINE LYMPHOCYTE BLASTOGEN ESIS PRIOR AND AFTER IN-VITRO SUPPRESSION BY DOG DEMODICOSIS SERUM USING ETHIDIUM-BROMIDE FLUORESCENCE ASSAY

The mitogen induced blastogenic response of lymphocytes from normal do gs and dogs with generalized demodicosis (GD) was measured by the ethi dium bromide (EB) fluorescence assay. Serum from GD dogs significantly suppressed the ill vitro reactivity to Con A of peripheral blood lymp hocytes (PBL) from normal dogs and GD dogs, however with a different p ercentage of suppression 40.6 and 81.2%, respectively. As a result, th e degree of lymphocyte blastogenesis suppression in GD dogs did not pa rallel the immunosuppressive potency of their serum (Tab. IV). The dat a indicate that PBL obtained from GD dogs did not respond to Con A as well in the presence of serum from normal dogs as did PBL from normal dogs (Tab. IV). In one third of examined GD dogs a similar situation w as described also by Hirsh et al. (1975). The basis for this cellular modified response is unknown. It does not appear that the age or the c hronicity of the disease are related to this observation. Further stud ies are necessary to elucidate this relation. The GD dogs showed not o nly a significant depression of the lymphocyte response to Con A but a lso enhancement of the ability of unstimulated cells to proliferate wa s also observed (Tab. IV). Similar observation was reported by others (Barriga et al., 1992). The meaning of this is not clear al present. T his finding is discussed in the light of proposed different effects of the parasite or the host's reactivity to the parasite on different su bsets of lymphocytes. No significant difference of PBL responsiveness to Con A between healthy dogs with respect to the age (Tab. III) and t he time of examination (compare results in Tabs. I and IV) was observe d. Autologous serum showed a better responsiveness of normal canine ly mphocytes to Con A than fetal calf serum (FCS). It is suggested that t he use of FCS might lead to an erroneous judgement (Tab. I). Both lect ins, Con A and PHA induced cell proliferation of healthy dogs in very similar amount (Tab. II). Our results indicated that EB fluorescence a ssay is a useful method for detection a respondence of canine lymphocy te blastogenesis.