Enhancement of murine bone marrow colony formation and L-transformation by Brucella antigen.

Brucella melitensis and Pseudomonas aeruginos antigens, in the form of heat-killed cells, enhanced serum stimulation of colony formation by mouse bone marrow progenitor cells. The antigens also enhanced colony formation in unstimulated medium. Prior sensitization of the C57BL mice by recent infection or by immunization six months earlier increased sensitivity of bone marrow cells to brucella antigen enhancement of colony formation. The immunized mice provided marrow cells more primed to colony formation than infected mice. Evidence is presented that antigen also leads to greater recovery of live brucellae from marrow cells of infected animals. This may be due both to stimulation of the marrow cells and to direct stimulation of the brucellae in those cells. L-forms of brucellae from stimulated marrow cell cultures were isolated. Some degree of stabilization of the L-form was accomplished through incorporation into the marrow culture medium of MgSO4, sucrose and penicillin G. The place in the infection process of L-forms is discussed in terms of the hypothesis that the L-form is a product of immune reactions that involve a step-wise degradation of the brucella cell wall during which the various cell-mediated immune reactions become operative and are themselves the reflection of a general stimulation by the brucellae of the hemopoietic and lymphopoietic systems.