Nude mice from homozygous nude parents show smaller PFC responses to sheep erythrocytes than nude mice from heterozygous mothers

Abstract

THE congenitally athymic mouse which is homozygous for nude (nu/nu), compared with the phenotypically normal heterozygote (+/nu) or the normal mouse (+/+) is severely deficient in its plaque-forming cell (PFC) response to sheep erythrocytes (SE)^1,2. The minimal response of the nude is generally attributed to a deficiency of thymus-derived helper cells which are essential for a full PFC response to thymus-dependent antigens such as SE^1–3. The amount of helper activity (T cell or T-cell-like) that nude mice may receive from their mothers is of concern in several laboratories^4–9, since most nude mice obtained routinely are born of phenotypically normal (+/nu) mothers that have T cells. There is debate about the relative importance of T-cell precursors observed in nude mice¹⁰, which may be stimulated to express T-cell antigens by soluble factors¹¹, and the equally important possibilities that nudes may receive T cells and/or soluble factors in utero from their normal +/nu mothers or from their +/nu or +/+ littermates or from the colostrum of +/nu mothers¹². The results of studies designed to resolve this issue remain equivocal^14–13. There is a need¹² for studies with nude mice born of homozygous nude parents (nu/nu ♀ × nu/nu ♂) and raised by nude mothers to minimise the possibilities of transfer of functionally mature T cells in utero or the transfer of T cells or T-cell-like factors by the colostrum. So far this criterion has been difficult to meet since nude mothers from most common mouse strains were poorly fertile or could not raise their young¹⁴.