CR2 and infection: Whatever the mechanism, immunoglobulins secreted by the high proportion of effector CD2+CD21— AFC/PC cells and their resting CD2—CD21— AFC/PC progenies in the blood may explain the observed hypergammaglobulinemia in all immunoglobulin classes that characterize this infection in isolator and fetal piglets [6,7,28] and also the robust production of Abs in conventional animals [9,10].