Implantation of cultured thymic fragments in congenitally athymic (nude) rats

Summary Cultured thymic fragments correspond to the thymic microenvironment depleted of lymphocytes and dendritic cells. When these fragments are implanted under the kidney capsule of congenitally athymic rats, lymphocytes and dendritic cells of host origin enter the graft and induce thymus-dependent immunity in the recipient. This paper describes the ultrastructure of the fragments and the changes that occur during the restoration of normal thymic architecture. At the end of the culture period of 6–9 days and in the early stages after implantation, the grafts consist of keratin-containing epithelial cells of unusual morphology that can be labelled with antibodies raised against the epithelium of the mid/deep cortex and the subcapsule/medulla. Normal thymic architecture develops, including nerves and blood vessels, as lymphocytes populate the environment, and by 4–6 weeks the epithelial cells are the same phenotypically and ultrastructurally as those found in normal rat thymus. However, some areas without lymphocytes still contain the atypical epithelial cells seen before implantation. Large multinucleated giant cells are also present with a few associated epithelial cells of subcapsular/medullary phenotype. In conclusion, the cultured thymic fragments contain a hitherto unknown precursor epithelial cell with an atypical ultrastructure and phenotype that is not seen in normal development.     

Experimental mucormycosis in congenitally athymic (nude) mice

Athymic nude (nu/nu) mice and their phenotypically normal (nu/+) littermates displayed a similar susceptibility to acute lethal infection withAbsidia corymbifera. Although the clinical manifestations of acute infection were also similar in both groups, the nude mice tended to develop more extensive lesions and were less effective in eliminating viableA. corymbifera spores than their heterozygous littermates. The results suggested that thymus-dependent processes did not play an essential role in primary resistance to mucormycosis.     

Cortisone-sensitive, innate resistance to Hymenolepis nana infection in congenitally athymic nude rats

The innate resistance of the unnatural rat host to the mouse tapeworm Hymenolepis nana is cortisone sensitive but thymus independent. When congenitally athymic nude rats were orally given eggs, cysticercoids, or adult worms of H. nana, no lumenal adults were established except when they were treated with cortisone acetate during the expected lumenal development. The effect of cortisone to promote adult maturation in the rats was compared in nude and normal rats given eggs of H. nana. The fecundity of the worms (assessed by the fresh worm biomass and the number of infective eggs produced) was much higher in cortisone-treated nude rats than in cortisone-treated normal rats. When the nude rats reconstituted with thymocytes were given eggs and treated with cortisone, the fecundity of H. nana dropped to the same level as in cortisone-treated normal rats. It is strongly suggested that the unnatural rat host has thymus-independent cortisone sensitive resistance to an initial infection (which is the main component of the innate resistance and blocks the lumenal establishment of this parasite) and thymus-dependent resistance (which suppresses the established worms' fecundity and may be ascribed to acquired resistance to the ongoing infection).     

Immunosuppression of congenitally athymic (nude) mice with heterologous anti-immunoglobulin heavy-chain antisera

Congenitally athymic (nude) mice have been shown to be far more sensitive than their phenotypically normal littermates to immunosuppression by anti-Ig antisera. Anti-μ suppression of nude mice was seen to result in complete and stable loss of IgM and IgA as well as severe reductions in IgG1 and IgG2 levels. Anti-α treatment of nudes resulted only in complete and stable loss of IgA; similarly, anti-γ1γ2 treatment achieved only class-specific reductions of IgG1 and IgG2 levels, but these reductions recovered slightly during suppression. Nude mice were more severely immunosuppressed than their phenotypically normal littermates upon anti-Ig treatment and demonstrated much less ability to recover from such suppressive effects. The significance of these observations regarding thymus dependency of immunoglobulin synthesis in nude mice is discussed.     

Lack of susceptibility of congenitally athymic nude mice to human non-A, non-B hepatitis

Nude mice were inoculated intravenously with chimpanzee serum containing a human non-A, non-b hepatitis agent. Control groups of nude mice were inoculated with normal saline or normal chimpanzee serum. During 77 days of observation, evidence of non-A, non-B hepatitis was not detected. Serum alanine aminotransferase levels remained within normal limits, and normal liver histology was seen in serially killed mice.     

Mycoplasma pulmonis arthritis in congenitally athymic (nude) mice. Clinical and biological features

Congenitally athymic BALB/cA nu/nu mice were employed to elucidate the role of the thymus in experimental Mycoplasma pulmonis strain m53 infection, and nu/+ mice were used for comparison. Chronic polyarthritis was frequently produced in both of nu/nu and nu/+ mice by intravenous injection of the organisms. Macroscopically, nu/nu mice developed severer arthritis and a much lower grade of resolution than nu/+ mice. Periarticular abscess, conjunctivitis, and emaciation were observed in some of the nu/nu mice, but not in the nu/+ mice. Mycoplasmas were isolated from joints and other tissues (including periarticular abscesses and eyelids) of infected nu/nu mice at higher frequencies as well as in greater quantities, and did not show any elimination trends for at least 20 weeks after inoculation. However, nu/+ mice, mycoplasmas were almost exclusively located in joints, and distribution of organisms to the other organs disappeared soon after the infection. Increases in complement-fixing antibody titers were not related to the inhibition of mycoplasmal spread. Thymus-dependent functions that may in some way prevent growth and spread of mycoplasmas in mice are discussed.     

Hymenolepis nana: worm recovery from congenitally athymic nude and phenotypically normal rats and mice

When eggs or mouse-derived cysticercoids of Hymenolepis nana were inoculated into previously uninfected congenitally athymic nude (rnu/rnu) rats of an outbred Rowett strain, they failed to mature in the intestinal lumen. They also failed to mature in phenotypically normal (rnu/+) littermates, except when these hosts were treated with cortisone acetate from the beginning of the lumen phase. The Rowett rat, either thymus-deficient or not, was susceptible to tissue cysticercoids but resistant to luminal adults. It is therefore considered to be an unnatural host, at least for mouse-derived H. nana. There was little or no difference in susceptibility to initial tissue cysticercoids between these nude rats and phenotypically normal ones. The normal rats became completely resistant to reinfection with eggs and no secondary cysticercoids developed in their intestinal tissue, whereas the nude rats showed unaltered susceptibility to secondary tissue cysticercoids. Thus, acquired resistance to egg challenge, assessed by the failure of tissue cysticercoid recovery, was thymus-dependent. However, innate resistance to both a primary egg dose, assessed by the low recovery rates of tissue cysticercoids, and to a primary cysticercoid dose, assessed by the failure of luminal adult recovery, were thymus-independent. The effect of cortisone acetate to initiate maturation of H. nana appeared to be unrelated to thymus function. In contrast, all mice, either thymus-deficient or not, were highly susceptible to both phases. The number of worms recovered was more than 10 times greater than that of cysticercoids established in the rat's intestinal tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anti-mu induces lymphoma in germfree congenitally athymic (nude) but not in heterozygous (nu/+) mice

To further our understanding of the role of host immunity in the development of lymphoid neoplasia, groups of germfree BALB/c nude and nu/+ mice were either followed unmanipulated or were treated, beginning at birth, with anti-mu, normal goat IgG or with lipopolysaccharide (LPS). The survival and development of neoplasia of all groups of animals were monitored up to 2 yr. Nude mice, under germfree and specific pathogen-free (spf) conditions, had a higher incidence of lymphoid neoplasia and reduced survival when compared to nu/+ littermates. The incidence of lymphoid tumors in nude mice under spf or germfree conditions was 7.2 and 8.7%, respectively, in comparison to 0% in nu/+ animals. Treatment of germfree nude mice with anti-mu, but not with goat IgG, increased the incidence of lymphoid tumors to 39%. Anti-mu did not significantly change the incidence of lymphoid neoplasia in nu/+ animals. Treatment of nu/nu and nu/+ mice with LPS, however, led to a several-fold increase in the appearance of neoplasia, to values of 25.4% in nude and 10% in nu/+ mice. Lymphoid neoplasia found in either unmanipulated, anti-mu, or IgG-treated germfree or spf mice included Thy-1.2+, surface IgM+, and IgG+ tumors. In contrast, all the lymphomas found in LPS-treated mice were surface IgM+. Thus, whereas LPS may have generated a relatively homogeneous group of tumors, anti-mu may have randomly increased the normal incidence of spontaneous tumors. Moreover, although there was significant variation in the histologic appearance of tumors, both within treatment groups as well as in different areas of the same animal, only LPS-treated mice were regularly noted to have distant nonlymphoid involvement, with lesions found in liver, lung, and kidney. In contrast, the incidence of nonlymphoid neoplasia was similar and was less than 2.5% in all groups.     

Induction of macrophage Ia expression by lipopolysaccharide and Listeria monocytogenes in congenitally athymic nude mice

Experiments were performed to analyze the mechanism by which lipopolysaccharide (LPS) modulates the expression of Ia by murine peritoneal macrophages in vivo. We investigated the effect of LPS on Ia expression in T cell deficient mice by using the congenitally athymic nude mouse model. Injection (i.p) of LPS into athymic (nu/nu) mice resulted in a dramatic increase in the expression and biosynthesis of Ia by peritoneal macrophages 7 days after injection. The magnitude and kinetics of this induction were equivalent to increases observed after LPS injection of euthymic (nu/+) mice. Viable Listeria monocytogenes also increased Ia expression in athymic mice, but in contrast to the induction observed in euthymic mice at 3 and 7 days after injection, increased Ia expression was not seen until 7 days. Ia induction by either LPS or L. monocytogenes in athymic mice was not due to the presence or development of mature T cell function as defined by assays for T cell mitogenesis and interleukin 2 production. We conclude that increased macrophage Ia expression by LPS and L. monocytogenes in vivo can occur in the absence of mature functioning T cells.     

In vivo generation of suppressor T cells by thymosin in congenitally athymic nude mice

Treatment of nude mice with thymic factors such as thymosin has been mostly ineffective in generating effector T cells. This study examined the effects of treating nude mice with thymosin fraction 5 on the induction of cells that could participate in and/or regulate cytotoxic T lymphocyte (CTL) generation by normal spleen cells in vitro. Splenic lymphocytes from BALB/c nude mice injected with thymosin fraction 5 every other day for 2 wk were tested for their ability to generate CTL in vitro. Two days after the last subcutaneous injection of thymosin, nude spleens were removed, mixed with normal BALB/c spleen cells, and placed into a mixed lymphocyte tumor culture (MLTC) against allogeneic RBL 5 tumor cells. After a 5-day incubation, cultures were tested for the presence of CTL in a 4-hr 51Cr-release assay. Spleen cells from thymosin-treated nude mice did not generate CTL but suppressed the ability of normal spleen cells to generate CTL in vitro. Characterization of the thymosin-induced nude mouse suppressor cells showed them to be Thy 1 positive, nonadherent, cyclophosphamide-sensitive T cells. These data demonstrate that some T cell maturation occurs in vivo under thymosin influence. However, the activity of these cells is initially limited to a regulatory function. These studies suggest that maturation of functional suppressor T cells occurs before CTL. Further immunologic manipulation appears to be necessary in order to induce CTL effector cells in nude mice.     

Effect of immune reconstitution on resistance to Brugia pahangi in congenitally athymic nude mice

The dichotomy of resistance to Brugia pahangi (Nematoda: Filarioidea) between nonsusceptible, euthymic C3H/HeN mice, heterozygotic for the "nu" gene (+/nu), and susceptible, congenitally-athymic "nude" (nu/nu) C3H/HeN mice, suggests that resistance is thymus-dependent. To test this hypothesis, the effect of syngeneic neonatal thymus grafts and neonatal thymus cell suspensions on recovery of worms at day 40 PI, and responses to Concanavalin A (Con A) were examined in reconstituted nudes. Nude recipients of a thymus graft 7 or 14 wk before subcutaneous inoculation with 50 infective larvae (L3) yielded no worms and responded strongly to Con A. Serum from these mice reacted in two lines of identity with serum from similarly-infected heterozygotes by double radial immunodiffusion against an adult worm saline extract. Nude recipients of a thymus 2 days or 3 wk before inoculation harbored an average of three or two worms, respectively. Intravenous injection of nude recipients with 10(7) or 10(8) neonatal thymus cells seven weeks before inoculation was less effective in conferring resistance to B. pahangi and responsiveness to Con A. Complete resistance to B. pahangi could be adoptively transferred to nude mice by 10(8) spleen cells obtained from infection-primed heterozygotes and injected intravenously on the day of larval inoculation. The same numbers of worms were significantly reduced. less effective when injected 3 wk before inoculation, although numbers of worms were significantly reduced. Passive transfer of primed heterozygote serum, containing high titers of antibodies to adult worm and larval antigens, failed to protect nude recipients against a larval inoculum in the absence of cellular reconstitution.(ABSTRACT TRUNCATED AT 250 WORDS)     

The elimination of mouse hepatitis virus by temporary transplantation of human tumors from infected athymic nude mice into athymic nude rats (rnuN/rnuN).

A nude mouse colony held in an isolation unit was found to harbor MHV despite the fact that all hygienic precautions were taken. The virus spread rapidly causing a high mortality rate predominantly in experimental animals. Moreover, we observed a high percentage of tumor regression in our tumor transplanted mice. Attempts to eliminate the MHV by repeated tumor transplantation into virus-free nude mice were unsuccessful. Since MHV has a limited host range, we transplanted, in parallel, four different lines of embryonic renal tumors (three triphasic nephroblastomas and one malignant rhabdoid tumor of the kidney) from athymic mice into athymic rats and fragments of the same tumors into "fresh" nude mice. All manipulations were performed in isolators. Detection of MHV was done twice by serological examination of six-week-old sentinels. The results showed transmission of MHV infection in the control mice under gnotobiotic conditions as previously found in the normal animal room. On the other hand, there was no evidence of infection, neither in the transplanted nude rats nor after retransplantation of tumors into nude mice. We hypothesize that the virus is harbored in the stromal cells of the murine host but not of the rat host nor in the human tumor cells. Histological comparison showed no alteration of specific tumor morphology in the different hosts.     

A review of scalp split-thickness skin grafts and potential complications

A review of 113 patients who underwent 178 scalp split-thickness skin graft procedures is presented. Although our study confirms some of the work of previous authors, we found that the scalp donor site has potential complications which should be considered. These complications are minor in the adult population. In the pediatric population, however, excessive blood loss due to the relatively large surface area of the scalp limits the use of the scalp as a preferred donor site.