Quantitative studies of the adoptive immunological memory in mice. I. An age-dependent barrier to syngeneic transplantation.

Antibody-forming cells suspended from a mouse spleen and transferred to intact animals of the same genotype face a barrier which severely affects their capacity to implant and/or to function. This phenomenon was quantitatively studied in a model system which, utilizing the immunogenic properties of human serum albumin in mice, allows the secondary response of the transferred cells to be followed without interference from the host's own reactivity. The barrier to syngeneic transplantation was found (a) to be radiosensitive (500 R X-rays to the recipient abolishes it and insures optimal functional conditions to the donor cells) in the same order of magnitude of other mammalian systems involving rapidly dividing cell populations, and (b) to depend upon the age of the recipient: its linear rise is documented from birth time (when approximately 50% of the maximal immune capacity of the transfer is expressed) to the age of 2 months ( approximately 1 %). The significance of these findings to the immune response and to cell growth and differentiation is discussed.