The production of a lymphocyte inhibitory factor (LyIF) by bursal and thymic lymphocytes.

In this study the migration and migration inhibition of different lymphoid cell populations from immunized and control birds were evaluated. Bursal, thymic, and splenic cells migrated in a capillary tube with thymic cells forming the characteristic cone of cells within 4 hours of culture. Both thymic and bursal cell populations from birds sensitized by Mycobacterium tuberculosis produced a lymphocyte inhibitory factor (LyIF) when stimulated by specific antigen in vitro. The ability of bursal cells to release LyIF declined subsequent to 10 weeks of age while LyIF was not apparent in thymic lymphocytes until 9 weeks of age and remained high until 27 weeks of age. The active material generated in specifically stimulated cultures from sensitized bursal cells appeared to be antigen dependent whereas thymic cell mediator is antigen independent. The production of LyIF in chickens, while correlating with delayed type hypersensitivity, does not solely reflect T-cell function but B-cell response as well.