Experimental Farmer’s Lung: Immunological Response in the Rabbit to Protein Fractions of Micropolyspora Faeni

Groups of rabbits were subjected to one, two and three intratracheal exposures to a crude culture of Micropolyspora faeni (Mf). Another group was immunized by a single subcutaneous injection of Mf in complete Freund's adjuvant. The immune response was evaluated by in vitro lymphocyte stimulation tests, agar gel precipitation tests and Prausnitz-Küstner reactions, using as antigens a whole soluble Mf extract (glycine extract) and different protein fractions obtained by Chromatographic fractionation on Sephadex G 150.

Our results suggest the development of an active cell-mediated response soon after the first intratracheal exposure, the humoral response becoming stronger only after 2 or 3 exposures. Skin sensitizing antibodies were found only in one intratracheally exposed rabbit after 3 exposures.

Although great individual variations in the immune response were observed after intratracheal exposure, our results suggest that the high molecular weight protein fractions of the M. faeni extract are the most immunogenic. Following subcutaneous immunization, on the other hand, the immune response is more homogeneous and is directed against a larger variety of Mf-antigens.