Homograft-reactive large mononuclear leucocytes in peripheral blood and peritoneal exudates

¹ Division of Biological and Medical Sciences, U.S. Naval Radiological Defense Laboratory, San Francisco, California

Two criteria have been employed for demonstrating the presence of homograft-reactive cells in peripheral blood and peritoneal exudates: a) production of a lethal wasting syndrome in sublethally x-irradiated (500 r) (LxA)F₁ hybrid mice following injection of cells from parental strain (A-strain) donor mice; b) abrogation of protection by injected bone marrow in lethally x-irradiated mice by these cells. Injection of 8 x 10⁶ peritoneal exudate granulocytes does not elicit the wasting syndrome, whereas 2.1 x 10⁶ mononuclear cells obtained from peritoneal exudates 8 days after mineral oil administration are reactive. When peritoneal mononuclear cells from isoimmunized A-strain donors were administered, reactivity of cells was enhanced. Prior treatment of A-strain donor mice with cortisone did not abolish homograft reactivity of injected blood (1.1 x 10⁶ nucleated cells). Under these conditions of cortisone treatment, there was a relative increase in frequency of large mononuclear cells (9 µ diameter or larger), disappearance of essentially all small lymphocytes (5 µ diameter). Data are presented that indicate the capacity of large mononuclear cells in peripheral blood to transform into cells of plasma cell series. It is concluded that circulating blood contains a mobile pool of large mononuclear cells capable of division, and potentially able to initiate immunological reactions, i.e. homograft reactions, analogous to that possessed by lymphoid tissue cells.