Lymphocyte depletion of murine fetal thymus and subsequent chimeric recolonization in vitro

Thymus from 14-day murine fetuses, maintained in organ culture, was depleted of lymphocytes when incubated for 7 days at room temperature (24 degrees C) in a gas mixture of 10% CO2 in air or 10% CO2 in O2. Shorter incubation resulted in sparing of some lymphocytes and/or their precursor populations. Cultures grown in CO2 in air maintained their Ia-positive cell population, as demonstrated in single cell suspensions, while those grown in CO2 and O2 appeared to lose Ia-positive cells. When recolonized by fetal liver (FL) the thymuses became fully lymphoid again in organ culture. Depending on the degree of lymphocyte depletion, split chimerism at various levels could be produced, when the FL used was from a strain allogeneic to the thymus.