Thymus independence of eosinophilia induced by a non-parasite antigen.

Eosinophilia is primarily a T-cell-dependent phenomenon, related to helminthic infections. Using a rat model (+/rnu), it has been shown that keyhole limpet hemocyanin (KLH) in complete Freund's adjuvant (CFA) induced blood eosinophilia, but only after pretreatment with cyclophosphamide (CY). CY alone caused an eosinophilopenia which was reversed by CFA or KLH-CFA treatment. Eosinophilia was also induced in congenitally athymic rnu/rnu rats after CY pretreatment and KLH-CFA stimulation, the response being of a similar order as that in +/rnu animals. It is concluded that a non-parasite antigen can induce blood eosinophilia after pretreatment with CY, the response being thymus-independent. This model may be appropriate to study the biological significance of the eosinophil response.