Neonatal injection of mice with rabbit anti-µ antiserum has been shown to produce complete loss of direct and indirect plaque-forming responses to sheep erythrocytes as well as loss of serum IgM and severe depressions of all other serum immunoglobulins. Similar injection of anti-γ1γ2 or anti-γ1 antibodies effects a loss of the indirect response but induces relatively minor alterations in serum Ig levels. Delaying initiation of anti-µ treatment until young adulthood results in a somewhat diminished effect on plaque-forming responses and serum Ig levels but triggers the release of high serum levels of an aberrant µ-bearing protein. Anti-µ suppression of genetically thymusless mice indicates that at least part of the target cells for suppression are bone marrow derived. A working hypothesis for the maturation of humoral antibody-producing cell lines as it relates to these data is discussed.

Splenic gamma delta T cells (CD4-, CD8-) increased more than 10-fold upon resolution of either Plasmodium chabaudi adami or P.c. chabaudi infections in C57BL/6 mice compared to controls. Similarly, a 10- to 20-fold expansion of the gamma delta T cell population was observed in beta 2-microglobulin deficient (beta 2-m0/0) mice that had resolved P.c. adami, P.c. chabaudi or P. yoelii yoelii infections. In contrast, increases in the number of splenic alpha beta T cells in these infected mice were only two to three-fold indicating a differential expansion of the gamma delta T cell subset during malaria. Because nucleated cells of beta 2-m0/0 mice lack surface expression of major histocompatibility complex class I and class Ib glycoproteins, our findings suggest that antigen presentation by these glycoproteins is not necessary for the increasing number of gamma delta T cells. Our observation that after resolution of P.c. adami malaria, C57BL/6 mice depleted of CD8+ cells by monoclonal antibody treatment had lower numbers of gamma delta T cells than untreated controls suggests that the demonstrated lack of CD8+ cells in beta 2-m0/0 mice does not contribute to the expansion of the gamma delta T cell population during non-lethal malaria.

Congenitally a t h y m i c (nude) mice h a v e been shown to accept skin allografts p e r m a n e n t l y (1-4). I t has been further established that these mice accept skin grafts from several other species of rodents and lagomorphs, including rats, hamsters, and rabbits (5, 6). W e have recently reported t h a t nude mice will m a i n t a i n for their lifetime full thickness grafts of normal h u m a n skin (7). This acceptance of h u m a n skin p r o m p t e d us to a t t e m p t xenografts of ever increasing phylogenetic disparity in order to determine w h e t h e r these athymic mice possess any ability w h a t s o e v e r to reject foreign skin. W e report here that nude mice m a i n t a i n indefinitely intact skin grafts not only from distantly related m a m m a l s (cat, human), but from birds (chicken) as well. T h e y also fail to reject skin grafts from reptiles (fence lizard and chameleon) and from amphibians (tree frog), although such grafts undergo certain morphological changes. Materials and MethodsMice.--Congenitally athymic mice, hereafter designated nude, were selected from a stock which has been backcrossed into the BALB/c strain. Nude mice and their phenotypically normal littermates were maintained on sterilized Purina 5010C feed (Ralston Purina Co., Inc., St. Louis, Mo.) and acidified-chlorinated water.Skin Grafling.--Skin grafting was performed on mice of both sexes between 5-7 wk of age.Human skin was obtained from the foreskins of circumcised infants; cat skin specimens were taken from the ear, paw, and facial regions. Chicken skin grafts were prepared primarily from the cervical apterium (featherless skin) and its borders. A select few chicken grafts were prepared from the capital pteryla (contour feather tract) to include a maximal number of feathers or follicles; the feathers were plucked or trimmed 2 days before sacrifice for grafting. Skin from the large-scaled lizards (fence lizards, genus Sceloporus) was taken from the throat or abdominal regions, whereas that from the small-scaled lizards (chameleon, genus Anolis) and tree frogs (genus Hyla) was taken from any area of the trunk. All donor skins were prepared by pinning the entire specimen on a flat surface and gently scraping away all subcutaneous fascia. Circular grafts 1 cm in diameter were then cut with a carefully sharpened, sterile cork borer.

Transplantation of involved psoriatic and nonpsoriatic human skin onto congenitally athymic (nude) mice has been performed successfully. Although biopsies at selected intervals demonstrate that the excess glycogen deposition normally seen in psoriasis is no longer consistently present, the psoriatic grafts did retain the usual characteristic histologic differences throughout the life of the animal, up to 11 weeks. This grafting procedure potentially represents a useful method whereby the study of psoriasis can be made in a nonhuman, living system.