Efficient natural defense mechanisms against Listeria monocytogenes in T and B cell deficient allogeneic bone marrow radiation.

Radiation chimeras in the early phase after bone marrow transplantation are a good model to study the efficiency of the body's nonspecific defense system represented by macrophages, polymorphonuclear cells (PMN), and NK cells. These cell types are present in large numbers in spleen and liver at that time, whereas the specific immune system represented by T and B cells is functionally deficient. We previously reported enhanced activities in vitro of macrophages (and PMN) from recipient animals in an early phase after allogeneic bone marrow transfer. We here demonstrate that these activities result in enhanced spontaneous resistance against Listeria monocytogenes in vivo. We concluded that enhanced nonspecific immune functions can in part compensate for the defective specific immune system after bone marrow transfer.