The Nature of the Immunologic Inadequacy of Neonatal Rabbits as Revealed by Cell

It is generally accepted that the immunologic mechanisms of the neonatal animal are poorly developed and in some instances virtually non-existent. This immunologic inadequacy early in life has been related both to the limited ability of the neonatal animal to synthesize gamma globulin and to the immunologic inexperience of the organism. However, it has not been determined whether the underlying inadequacy is a lack of cells capable of antibody synthesis for whatever reason, or an environment within the animal incompatible with the immunologic function of potentially capable cells. The technique of transferring cells capable of an antibody response to recipient animals offered a possible approach to the study of the immunologic inadequacy of the neonatal animal. Either primary or secondary antibody responses have been elicited in adult x-radiated or normal homologous recipients (1) after the transfer of cells appropriately stimulated with antigen. It seems likely, on the basis of considerable immunologic evidence, that in these transfer experiments it is the transferred ceils that are primarily responsible for the observed antibody responses and that the adult recipients play a supporting or secondary role. If this is true, the performance of immunologically competent cells after their transfer to neonatal recipients should throw light on the nature of the inadequacy of the neonatal animal. If the inadequacy of the neonatal animal were merely the lack of immunologically competent cells, properly stimulated cells transferred to neonatal should make an antibody response, especially since the neonatal recipients would not be likely to react strongly to the transferred cells. On the other hand, if something needed to support immunologically active cells were lacking in the internal environment of the neonatal animals, or if these immature animals possessed a factor capable of interfering with immunologic processes, properly stimulated cells trans-