Natural antibodies to human lymphocytes in murine strains

Murine strains vary greatly in their content of natural antibodies to human lymphocytes; sera from NZB, B10.BR/TSn, DBA/J, and B10.S mice reacted with more than 90% of the panel of human lymphocytes, yet those from other strains did not react. These levels of natural antibodies to human lymphocytes did not correlate with the H-2 type of mice, but appeared to be a dominant character with incomplete penetrance. Since sera from germfree mice also contained natural antibodies to human lymphocytes, their formation was not influenced substantially by bacteria.