An in vitro reaction between labelled flagellin or haemocyanin and lymphocyte-like cells from normal animals.

Labelled bacterial flagellin and haemocyanin reacted with lymphocyte-like cells from several rat and mouse tissues. This reaction occurred at low temperatures and in the presence of sodium azide, conditions which inhibited uptake of labelled proteins by phagocytic cells. The reactive cells took up at least 40,000 molecules of labelled flagellin, and appeared to have a much greater capacity, since pretreatment with 10,000 times this amount of flagellin was required to inhibit the reaction. The flagellin and haemocyanin were firmly bound to the cells, possibly to immunoglobulin at the cell surface, since prior treatment with antisera directed against mouse immunoglobulin inhibited the reaction with lymphocytes from mouse spleen and peritoneal exudate. The number of reactive cells in spleen was proportional to the concentration of labelled protein. At a given concentration of labelled protein, however, the number of reactive lymphocytes was characteristic of each tissue. Spleen, lymph node and thoracic duct lymph contained a similar proportion of reactive lymphocyte-like cells, peritoneal exudate contained more, and thymus contained few if any such cells. Bone marrow contained a high proportion of reactive lymphoid cells which apparently reacted in a non-specific manner, since the uptake of labelled protein by these cells was not inhibited by anti-immunoglobulin serum.