Immune responses in spleen colonies. Clonal distribution of haemolytic plaque-forming cells.

Antibody-forming cells were found in autochthonous spleen colonies, repopulating the spleens of mice which had been exposed to mid-lethal doses of radiation and inoculation of sheep red blood cells. This was true only for the secondary response, where a proportion of colonies contained haemolytic plaque-forming cells in variable numbers, ranging from 1/10 to 1/10 nucleated cells within a given spleen. The frequency distribution of antibody-forming cells in colonies suggests a clonal growth at an exponential rate, with a generation time of about 7 hours. It is therefore possible to cultivate and study single clones of competent cells in readily accessible, anatomically distinct regions of the mouse spleen. The present data do not discriminate between the derivation of the antibody-forming clones from the original colony-forming cells, or from a cell seeded-in from the spleen tissue outside the colony.