Fetal Human Hemolytic Plaque‐Forming Cells

Abstract
Lymphoid tissues from 24 human fetuses were assayed for hemolytic plaque-forming cells (PFC) against a variety of erythrocyte targets. PFC against maternal and other erythrocyte antigens were commonly detected in human fetal liver, lymph nodes, spleen or thymus as early as 16 wk gestation and were usually more abundant in liver than in spleen after 16 wk gestation. Human fetuses apparently develop some forms of immunocompetence very early during gestation.