Stimulation of mouse lymphocytes by a mitogen derived from Mycoplasma arthritidis. II. Cellular requirements for T...

The mitogenic property of supernatants from M. arthritidis cultures (MAS) is shown to be nonsedimentable, nondialyzable, labile to 56 degrees C for 1 hr, and active against spleen cells from both normal and germfree mice. Both viable M. arthritidis and MAS were active for T lymphocytes because anti-Thy-1 antiserum and C eliminated responsiveness. Spleen cells enriched for T lymphocytes by passage over nylon columns lost responsiveness unless supplemented with a radioresistant adherent cell population that was shown to bear Ia antigens. Evidence is also presented that the genetic control of T lymphocyte responses to the mycoplasma mitogen was exercised at the level of the Ia-bearing adherent cells. Thus adherent cells from positive responder mouse strains, but not those from nonresponder mouse strains, restored the responses of T cells from F1 hybrids between responder and nonresponder strains.