Thymic lesions in fatal infectious mononucleosis

Thymic lesions were studied in 35 patients with fatal infectious mononucleosis (FIM) including 21 males with the X-linked lymphoproliferative syndrome (XLP) and 14 non-XLP patients. Six patterns based on the lymphocyte content and status of Hassall's bodies were observed: massive lymphoproliferation effaced the architecture and Hassall's bodies (HB) in 6 cases. Epstein-Barr virus (EBV)-laden B cells surrounded by cytotoxic T cells and natural killer cells were found in one of these cases. Only 5 of the 35 thymuses contained normal-appearing HB. Seven showed a moderate reduction in HB. Rarely, multinucleated giant cells and hyaline globules were seen where one might expect HB to reside. Plasma cells and macrophages were generally abundant. Eight displayed a marked depletion of HB. In 7, no HB were recognized. Massive necrosis was seen in one of these cases. Stress involution was encountered in only two patients, both of whom had sporadic fatal IM. Thymic lesions and alterations were similar but less extensive in sporadic FIM. These morphological studies, taken in context with clinical and experimental reports, suggest that destruction of thymic epithelium may contribute to the progression of immune defects seen in XLP following EBV infection. The destruction of HB that we observed was similar in appearance to lesions in several other immune deficiency disorders.

Variation of cooling rate and concentration of dimethyl sulfoxide on rabbit kidney function

Rabbit kidney function was assessed in vitro after cryoprotection with either 3 or 4 M dimethyl sulfoxide. The introduction and removal of the cryoprotectant was carried out in a stepwise progressive manner and the removal in a stepwise progressive manner with hypertonic mannitol solutions. This in vitro model can be shown to respond to various ischemic-like states resulting in poor or absent function. Active tubular transport can be demonstrated. It has been used by many authors as an intermediate step prior to the ultimate test of reimplant and contralateral nephrectomy. Variations in the rate of cooling at cryoprotection levels of 3 and 4 M dimethyl sulfoxide concentration (Me2SO) were carried out. In general, at 3 M concentration of Me2SO, creatinine clearance, sodium and glucose reabsorption are preserved with a fair degree of success after cooling to -10, -15, and -20 degrees C in our model, when the rate of cooling to these levels is 1.0 degree C/min. When a cooling rate of 0.5 degree C/min is used, renal function is significantly reduced whether the final temperature is -10, -15, or -20 degrees C. Control rabbit kidneys will tolerate 4 M concentration of Me2SO and give fairly good function. When cooled to -15 or -20 degrees C, there is poor function at 0.1 and 0.5 degrees C/min. Fair function is obtained at the rate of 1 degree C/min to -10 degrees C. Therefore, at cryoprotectant levels of 3 and 4 M Me2SO, kidney function as assayed by in vitro perfusion, is better when the cooling rate is 1.0 degree C/min.

The effects of polyinosinic:polycytidylic acid (pI:C) on the graft-vs-host (GVH) reaction. II. Increased NK-mediated rejection on C57BL/6 lymphocytes by (C57BL/6 X A)F1 mice

We previously demonstrated that treatment of (C57BL/6 X A)F1 (F1) recipient mice with polyinosinic:polycytidylic acid (pI:C) before injection with 30 X 10(6) C57BL/6 (B6) lymphocytes prevents both the immunosuppression and pathologic lesions typical of graft-vs-host (GVH) reactions. We now report the further characterization of this phenomenon. Donor spleen and lymph node cells were labeled with fluorescein in vitro and injected into pI:C-treated or untreated mice. Two days later, recipient splenocytes were analyzed for the presence of fluorescein-labeled donor cells by flow microfluorometry. Treatment of F1 mice with pI:C resulted in a sharp reduction in the recovery of labeled B6 but not A strain parental cells. Treatment with pI:C had no effect when syngeneic recipients were used, or when F1 cells were injected into A, B6, or F1 recipients. These results suggest that pI:C treatment induces rejection of B6 but not A or F1 lymphocytes by F1 hybrid mice at least as early as 2 days after donor cell transfer. As F1 cells are not rejected by either parent, rejection does not seem to be directed against classical alloantigens. These observations are compatible with the previously described model of hybrid resistance (HR) against bone marrow grafts. The rapidity of rejection strongly suggested that natural cytotoxic mechanisms were involved, thus, natural killer (NK) cell and macrophage (M phi) cytotoxic activities were tested throughout the time when the parental cell graft was being rejected. Over this period, pI:C treatment increased cytotoxic activity against the NK-sensitive target cell line YAC-1 but had no effect on spontaneous M phi tumoricidal activity against the L5178Y and MDAY-D2 cell lines. The results suggest that NK cells, but not M phi, may be involved in the elimination of B6 parental cells by the pI:C-treated F1 mice. NK cells have been demonstrated to be radioresistant; thus, as a test of our hypothesis, we examined the effects of irradiation on the capacity of pI:C treated F1 mice to reject B6 lymphocytes. The results show that this capacity was not blocked by 750 cGy, a dose of radiation that abrogates most T and B cell functions. Furthermore, rejection of parental cells could be prevented by treatment of recipient F1 mice with antibodies to asialo GM1, a treatment that suppresses NK activity. These data demonstrate that pI:C-mediated protection from GVH-induced changes is due to increased rejection of grafted B6 parental cells by F1 NK cells, a phenomenon very similar, if not identical, to HR to bone marrow grafts.

The effects of polyinosinic:polycytidylic acid (pI:C) on the graft-vs-host (GVH) reaction. II. Increased NK-mediated rejection on C57BL/6 lymphocytes by (C57BL/6 X A)F1 mice

We previously demonstrated that treatment of (C57BL/6 X A)F1 (F1) recipient mice with polyinosinic:polycytidylic acid (pI:C) before injection with 30 X 10(6) C57BL/6 (B6) lymphocytes prevents both the immunosuppression and pathologic lesions typical of graft-vs-host (GVH) reactions. We now report the further characterization of this phenomenon. Donor spleen and lymph node cells were labeled with fluorescein in vitro and injected into pI:C-treated or untreated mice. Two days later, recipient splenocytes were analyzed for the presence of fluorescein-labeled donor cells by flow microfluorometry. Treatment of F1 mice with pI:C resulted in a sharp reduction in the recovery of labeled B6 but not A strain parental cells. Treatment with pI:C had no effect when syngeneic recipients were used, or when F1 cells were injected into A, B6, or F1 recipients. These results suggest that pI:C treatment induces rejection of B6 but not A or F1 lymphocytes by F1 hybrid mice at least as early as 2 days after donor cell transfer. As F1 cells are not rejected by either parent, rejection does not seem to be directed against classical alloantigens. These observations are compatible with the previously described model of hybrid resistance (HR) against bone marrow grafts. The rapidity of rejection strongly suggested that natural cytotoxic mechanisms were involved, thus, natural killer (NK) cell and macrophage (M phi) cytotoxic activities were tested throughout the time when the parental cell graft was being rejected. Over this period, pI:C treatment increased cytotoxic activity against the NK-sensitive target cell line YAC-1 but had no effect on spontaneous M phi tumoricidal activity against the L5178Y and MDAY-D2 cell lines. The results suggest that NK cells, but not M phi, may be involved in the elimination of B6 parental cells by the pI:C-treated F1 mice. NK cells have been demonstrated to be radioresistant; thus, as a test of our hypothesis, we examined the effects of irradiation on the capacity of pI:C treated F1 mice to reject B6 lymphocytes. The results show that this capacity was not blocked by 750 cGy, a dose of radiation that abrogates most T and B cell functions. Furthermore, rejection of parental cells could be prevented by treatment of recipient F1 mice with antibodies to asialo GM1, a treatment that suppresses NK activity. These data demonstrate that pI:C-mediated protection from GVH-induced changes is due to increased rejection of grafted B6 parental cells by F1 NK cells, a phenomenon very similar, if not identical, to HR to bone marrow grafts.

Obliterative segmental sclerosis of pancreatic islets. A possible consequence of hypotensive shock in young BB rats

During the conduct of a time-course study of peripheral blood T lymphocytes in BB rats, a hitherto unreported islet lesion was recognized in 8 of 17 glucose-tolerant rats which had been subjected to repetitive cardiac puncture in early life and sacrificed at 186-190 days of age. Some of the large islets contiguous to fibrous septa demonstrated variable degrees of obliterative sclerosis and reduction of islet cell mass, associated with evidence of remote peri- and intrainsular hemorrhage. In 3 rats, additional features included an active, proliferative replacement of islet substance by fibroblasts and histiocytes. These islet alterations are not characteristic of BB rats, nor have identical lesions been described in studies of experimental or human diabetes mellitus. Affected rats had sustained repetitive episodes of blood loss (from 15% to 28% of total blood volume each time) during the early phase of the study. It is possible, but not proved, that hypovolemic shock was induced in some of these animals. Ischemic necrosis of islets has been reported in premature and young infants succumbing to shock. It is posited that hypovolemic shock in the young animal may, as in the infant, result in islet cell ischemic necrosis, sufficient to produce, with time, the described islet morphologic features.

Amplification of the graft-versus-host reaction by partial body irradiation

An experimental model has been developed for the study of combined effects of partial body irradiation (PBI) and graft-versus-host disease (GVHD) in which irradiation is delivered to the thorax 24 hr prior to induction of GVHD in hybrid mice by the injection of parental lymphoid cells. In mice irradiated to 1000 cGy or exposed to low doses of allogeneic lymphoid cells (20 X 10(6)), survival was 100% at 250 days. In contrast, combination of the two treatments, GVHD and PBI, resulted in a mortality of 83% and a mean survival time of 29 days, indicating synergy between GVHD and PBI. From histological studies of the lung it appeared that about 40% of the deaths occurring after combined GVHD/PBR treatment might be attributable to pneumonia. The cause of death in the remaining mice receiving combined treatment is not known. Mice receiving combined PBI/lymphoid cell treatment develop a characteristic skin lesion that is not seen in nonirradiated mice and is confined to the irradiated area. The effect of preinduction PBR on the timing and severity of GVHD is similar to that which would be produced by an increase in the number of effector cells.

The effects of polyinosinic: polycytidylic acid (pI:C) on the GVH reaction: immunopathological observations

The effects of polyinosinic: polycytidylic acid (pI:C) on the graft-versus-host (GVH) reaction were studied. The drug pI:C rapidly and markedly induces interferon and augments natural killer (NK) cell activity. GVH reactions were induced by injecting parental lymphoid cells intravenously into F1 hybrid mice. The development of a GVH reaction was monitored by measuring the plaque-forming cell (PFC) response to sheep red blood cells (SRBC) and by histological examination. When 30 X 10(6) B6 lymphoid cells were injected into B6AF1 mice, the recipients developed profound immunosuppression by 10-12 days post-GVH induction. In addition, pathological changes indicative of GVH reactions were seen in the spleen, lymph nodes, thymus, liver, lung, pancreas, and salivary gland of these mice. However, the treatment of B6AF1 recipients with pI:C prior to parental cell transfer markedly reduced the degree of suppression of the immune response, as measured by the PFC response to SRBC. Also, such mice failed to demonstrate the histological lesions of GVH disease. Treatment of donor mice with pI:C had no effect in preventing either GVH-induced immunosuppression or pathological changes. This study suggests that a pI:C-induced mechanism, possibly involving NK cells, is capable of regulating the GVH reaction.

The graft-versus-host reaction and immune function. III. Functional pre-T cells in the bone marrow of graft-versus-host-reactive mice displaying T cell immunodeficiency

Studies were performed to determine whether pre-T cells develop normally in the bone marrow of mice displaying thymic dysplasia and T cell immunodeficiency as a consequence of a graft-versus-host (GVH) reaction. GVH reactions were induced in CBAxAF1 mice by the injection of A strain lymphoid cells. To test for the presence of pre-T cells in GVH-reactive mice, bone marrow from GVH-reactive mice (GVHBM) was injected into irradiated syngeneic F1 mice and 30-40 days later thymic morphology and function were studied. Morphology studies showed nearly normal thymic architectural restoration; moreover, such glands contained normal numbers of Thy-1-positive cells. Functional pre-T cells were evaluated by transferring thymocytes from the irradiated GVHBM-reconstituted mice into T-cell-deprived mice. These thymocytes reconstituted allograft reactivity, T helper cell function and Con A and PHA mitogen responses of T-cell-deprived mice. These results suggest that the pre-T cell population in the bone marrow is not affected by the GVH reaction. Therefore, the T cell immunodeficiency associated with the GVH reaction is not due to a deficiency of pre-T cells in the bone marrow but is more likely associated with GVH-induced thymic dysplasia.

Genetics of the spontaneous diabetic syndrome. Interaction of MHC and non-MHC-associated factors

The occurrence of the spontaneous insulin-dependent diabetic syndrome in the rat is the result of several genetic susceptibilities. There is a requirement for the u haplotype of the rat major histocompatibility complex (MHC), RT1. More specifically this requirement is for genes mapping to the right of the RT1 A locus, which codes for class I products. Furthermore, u haplotypes from inbred strains other than the BB rat can provide this permissive u haplotype. Diabetes occurs in animals with either one or two u haplotype and the diabetic syndrome is similar in its characteristics. In addition to the requirement for the MHC genes, there are abnormalities of the immune system of the various diabetes-prone strains, which are present in animals that develop overt disease. These abnormalities segregate independently of the RT1 and interaction between the susceptibilities is necessary for the manifestation of the complete clinical syndrome.

The graft-versus-host reaction and immune function. IV. B cell functional defect associated with a depletion of splenic colony-forming units in marrow of graft-versus-host-reactive mice

Studies were conducted to determine whether a functional B cell defect occurred in the bone marrow of mice experiencing a GVH reaction (GVHBM). GVH reactions were induced in AxCBA F1 adult mice by an injection of A strain lymphoid cells. The GVH reaction was confirmed by immunosuppression and thymus histology. At various intervals after GVH induction, GVHBM was tested for its ability to restore B cell function in adult thymectomized irradiated mice reconstituted with normal thymocytes. GVHBM cells obtained seven days after GVH induction restored but slightly the plaque forming cell (PFC) response to sheep erythrocytes and the mitogen response to lipopolysaccharide (LPS). GVHBM cells obtained 10 days or later failed to reconstitute the PFC or LPS responses. GVHBM cells suppressed neither the T or B cell function of normal spleen cells nor the LPS mitogen response of normal bone marrow cells. In addition, the splenic colony-forming units (CFU-s) in GVHBM were slightly decreased by day 10 after GVH induction and markedly depressed by day 22 after GVH induction. These results suggest that the GVH reaction may affect two different events in B cell differentiation. The early decrease in functional B cells that occurs before there is any change in the CFU-s population suggests a direct effect on B cell production, whereas the later absence of functional B cells could be due to the marked decline in stem cell production (CFU-s).

Fetal rat intestinal transplantation: cryopreservation and cyclosporin A

Successful preservation of small bowel by cryobiologic techniques would increase the feasibility of intestinal transplants. Immunosuppression by Cyclosporin A (CyA) has also increased interest in intestinal transplantation. We have investigated the effect of cryopreservation and immunosuppression in fetal rat intestinal transplantation. Segments of fetal bowel implanted isogeneically into the paravertebral gutter of young rats were found to grow in a high percentage of animals (53% to 100%). Segments frozen to -20 degrees C or -40 degrees C at two rates of cooling, grew isogeneically (50% to 89%), demonstrating the feasibility of cryopreservation. Histologic examination of this bowel showed preservation of structure. When these segments were cooled and implanted allogeneically, no immunosuppressive effect was found. Segments protected by daily CyA administration grew. No synergistic effect was seen by associating CyA and cryopreservation. These experiments suggest the possibility of creating fetal small bowel long-term banking.

The functional and histological basis for graft-versus-host-induced immunosuppression

The GvH reaction resulting from the injection of parental strain cells into adult F1 hybrids suppresses both cell-mediated and humoral immune responses and is dependent on the donor-host combination and the number of parental cells used to induce the GvH reaction. The early suppression is due, at least in part, to the increased number of macrophages and the activation of suppressor macrophages which act directly on the T-helper cell and perhaps the B-cell as well. The macrophage suppression is associated with an increase in PGE production. The long-term T-cell immunodeficiency is mediated by GvH-induced thymic dysplasia resulting in a block or an arrest in T-cell differentiation and deficient IL-2 production. The B-cell immunodeficiency is associated with both a decrease in B-cell production from lymphoid progenitors and a decrease in CFU-s production. The GvH reaction induces 2 types of thymic lesion, a stress-related effect causing atrophy of the thymic cortex and a cytolytic process causing severe-to-moderate lesions in the thymic medulla as a consequence of injury to medullary epithelial cells and a loss of Hassall's corpuscles (thymic dysplasia). By employing the NK-cell-deficient beige mutation, it was shown that the severe-to-moderate thymic medullary lesions occurred in F1 mice only in those transplant situations in which the donor inoculum was of the +/bg genotype, regardless of the genotype of the recipient. It is proposed that activation of parental T cells may contribute to the early immunosuppressive events; however, the relatively permanent immunosuppression appears to be associated with NK-like effector cells which are capable of causing injury to lymphoid and epithelial tissue, especially epithelium of the thymic medulla. These studies raise the possibility that the GvH reaction may contribute to some T- and B-cell immunodeficiencies observed in the SCID and AIDS syndromes, as well as in patients following bone marrow transplantation.

Shock-related injury of pancreatic islets of Langerhans in newborn and young infants

Variable degrees of injury of the pancreatic islets of Langerhans, with sparing of the acinar pancreas, were observed in three infants (age range, 1 day to 3 months) who died of profound shock. The duration of shock varied from 19 to 48 hours. In two of the infants, the shock stemmed from hypovolemia; in the remaining infant, the shock followed blood loss, sepsis, and heart failure. The islet lesions were devoid of cellular infiltrates, hemorrhage, and fibrin thrombi. Tissue manifestations of shock included acute renal tubular necrosis, massive hepatic centrilobular necrosis, ischemic enteropathy, and "shock" lung. Study of pancreatic sections from 30 children (age range, 13 hours to 15 years) with clinical and/or morphologic evidence of shock showed no additional instances of islet injury. These findings suggest that pancreatic islets in the young may be vulnerable to shock-induced ischemia. Studies are in progress in an animal model to test this hypothesis.

Effects of cyclosporine on glucose tolerance in the rat

In a study of prevention of spontaneous diabetes in BB rats by therapeutic doses of cyclosporine (10 mg/kg/day), the male control non-diabetes-prone rats showed glucose intolerance after a 0.25 g/kg glucose load by gavage, at 90 and 130 days of treatment. Non-BB male Wistar rats treated similarly showed glucose intolerance at 1 wk of treatment, with progressive worsening for 5 wk, then sustained up to 12 wk of treatment. Fasting euglycemia was maintained, but both pre- and postchallenge plasma insulin levels were significantly lower with cyclosporine at several time points. Total pancreatic insulin was decreased to one-third that of control after 5 wk. After withdrawal of cyclosporine, glucose tolerance returned to normal in 2 wk. Sprague-Dawley rats responded similarly and in both strains, an increase in the cyclosporine dose to 15 mg/kg/day augmented the glucose intolerance. These results demonstrate that therapeutic doses of this agent induce reversible glucose intolerance due, in part, to inhibition of insulin secretion and also possibly inhibition of synthesis, though a peripheral effect is not excluded. This hyperglycemic effect of cyclosporine has implications for its potential use in type I diabetes mellitus, transplantation, and other autoimmune disease.

Association of spontaneous thyroiditis with the major histocompatibility complex of the rat

Overt insulin-dependent diabetes mellitus in the rat is associated with the u haplotype of the rat major histocompatibility complex (MHC), RT1. Thyroiditis of sufficient severity to result in elevation of TSH levels is seen in Buffalo rats (RT1b). In order to examine the association of autoimmune thyroid disease with MHC gene products, we have crossed inbred Buffalo rats with diabetic BB rats and examined the RT1 genotype, the histology of thyroid and pancreatic tissue, and two indices of thyroid function. The data indicate that animals having pancreatic lymphocytic infiltration and insulinopenic overt diabetes mellitus had at least one RT1u haplotype. All but one animal having severe histological thyroid lymphocytic infiltration had at least one RT1b haplotype. Rats with severe thyroiditis had higher mean TSH levels than rats with normal histology or rats with mild thyroiditis. We conclude that gene products of the rat MHC affect the severity of spontaneous organ-specific autoimmune disease in terms of clinically apparent as well as tissue inflammatory disease.

Histological and cytogenetic findings in a malignant tumor of the chest wall and lung (Askin tumor)

This report describes a histological and cytogenetic study of a malignant tumor involving the chest wall and lung (Askin tumor) of a young girl. Although initially considered to represent a variant of Ewing's sarcoma, immunocytochemical studies disclosed neuron-specific enolase in neoplastic cells. Ultrastructural study revealed rare cells which contained microtubules and/or dense core neurosecretory type granules. Cytogenetic analysis of neoplastic cells disclosed a reciprocal translocation (11;22)(q24;q12) and occasional extrachromosomal structures interpreted as double minute chromosomes. The latter finding, an indication of gene amplification, is commonly identified in neural crest-derived neoplasms. These ultrastructural, immunocytochemical, and karyotypic data provide evidence in support of a neuroepithelial histogenesis for the Askin tumor.

Malignant myoepithelioma (myoepithelial carcinoma) of the breast: an ultrastructural and immunocytochemical study

This report describes the light (LM) and electron microscopic (EM) features and the results of an indirect immunofluorescence study (IF), the latter using monoclonal and monospecific antibodies to cytoskeletal proteins, of a malignant, invasive and metastatic breast myoepithelioma. A 53-year-old female underwent mastectomy for a large necrotic mammary tumor that had invaded the overlying skin. By LM, the neoplasm was composed of interlacing bundles of large, elongated and interspersed stellate cells with acidophilic cytoplasm. The neoplastic cells displayed a moderate degree of anaplasia, high mitotic activity, and strong tendency for necrosis. Stromal desmoplasia was marked, especially toward the center of the neoplasm. By IF, the tumor cells revealed bright cytoplasmic fluorescence with antibodies to actin, prekeratin, and cytokeratin. A few scattered spindle cells, which stained with the anti-vimentin and anti-actin anti-bodies, most likely represented stromal myofibroblasts. The anti-desmin reaction was negative. By EM, the neoplasm was composed of variably differentiated, elongated and stellate myoepithelial cells connected by desmosomes, enveloped by remnants of basal lamina, and containing pinocytotic vesicles, a well-developed rough endoplasmic reticulum, large Golgi areas, aggregates of intermediate filaments that were often arranged in dense curvilinear bundles (tonofilaments), and bundles of microfilaments with fusiform, dense bodies. The combined LM, EM, and IF study of this mammary tumor establishes its myoepithelial origin and, thus, identifies it as myoepithelial carcinoma distinct from other spindle cell breast tumors. This neoplasms was locally invasive and cytologically malignant; moreover, its malignancy was further confirmed by the development of lung and pleural metastases.

Myofibroblastic stromal reaction in carcinoma of the breast: variations of collagenous matrix and structural glycoproteins

The matrix of mammary dysplasia, noninvasive ductal carcinoma, and invasive lobular and ductal carcinoma was analyzed by indirect immunofluorescence using antibodies to types I, proIII, III, and IV collagens, and laminin and fibronectin. Types proIII and III collagens were present in increased amounts in invasive carcinomas and were most abundant in the "young" edematous mesenchyme, areas corresponding to the peripheral invasive cellular front. Type I collagen was distributed throughout the matrix of invasive carcinomas but was most prominent within the central sclerotic zone of the neoplasms. Mammary dysplasia and noninvasive ductal carcinomas showed a uniform fibrillar and granular distribution of all types of collagen. In all but two cases of invasive carcinoma, staining with anti-laminin and anti-type IV collagen demonstrated the loss of basement membranes around tumor cells. In contrast, fluorescence pattern in noninvasive ductal carcinoma and dysplasia revealed an intact basement membrane. The distribution of fibronectin was similar to types proIII and III collagen. These findings support and extend our previous studies which suggested an analogy between the dynamics of matrix changes in granulation tissue and invasive carcinomas. These data also strengthen the concept that the myofibroblast could be a pivotal cell involved in the synthesis and redistribution of matricial proteins. The loss of basement membrane in invasive carcinomas appears to be an initial step for inducing the matricial alterations.

Mammary carcinoma arising in mice undergoing a chronic graft-versus-host reaction

A graft-versus-host reaction (GVHR) was induced in 30 (CBA X A)F1 mice by the iv injection of 50 X 10(6) parental strain A lymphoid cells. Solid tumors emerged in 5 of 10 experimental animals that survived beyond 14 months after the GVHR was initiated. The neoplasms were judged to be mammary carcinomas by light and electron microscopic examinations. C-type RNA viral structures were observed in some tumor cells. The neoplasms were successfully transplanted into syngeneic animals by either sc or ip injections of tumor cell suspensions. Tumor transfer to syngeneic mice was not possible if only spleen cells from tumor-bearing animals were transferred. No tumors developed in an age-matched control group that received no treatment.

Precocious thymic involution manifest by epithelial injury in the acquired immune deficiency syndrome

Thymuses from six heterosexual Haitian patients with the acquired immune deficiency syndrome (AIDS) were studied by light microscopy and the findings were compared with those from three control groups. The control groups included 1) five age-matched Haitian hospital patients; 2) ten age- and sex-matched Montreal patients who had died suddenly or had had brief illnesses; and 3) 20 middle-elderly Montreal patients who had experienced chronic, wasting illnesses or prolonged hospitalization. Thymuses from patients with AIDS demonstrated pronounced involution, effacement of the cortex and medulla, marked thymocyte depletion, variable degrees of plasma cell infiltration and fibrosis, and, above all, absence of Hassall's corpuscles. Thymuses from Haitian and Montreal control subjects who had died suddenly or had brief illnesses demonstrated minimal involution and abundant Hassall's corpuscles. Although thymuses from 12 of the chronically ill control subjects demonstrated marked involution, architectural effacement, and absence of Hassall's corpuscles, partial architectural preservation and variable numbers of Hassall's corpuscles were observed in eight of these subjects. Thus, the extent of thymic involution observed in patients with AIDS antedates that incurred with aging and supersedes that induced by sustained stress and inanition. The loss of Hassall's corpuscles in patients with AIDS suggests that the thymic epithelium either incurs a form of injury or undergoes precocious involution during the illness. Whether this lesion is central to the pathogenesis of AIDS or merely a reflection of intense, sustained stress coupled with accelerated physiologic involution is unknown. It is possible that the disappearance of Hassall's corpuscles may indicate important, although as yet cryptic events within the thymic microenvironment in this syndrome.

Pancreatic cellular infiltrates in autoimmune-prone New Zealand Black mice

Healthy New Zealand Black (NZB) mice of both sexes (age 19-31 weeks) were studied to determine the magnitude of pancreatic beta cell injury related to mononuclear cell infiltration of islets. This investigation was undertaken following the description of spontaneous cellular immune reactions against islets in four strains of autoimmune-prone mice, including NZB mice [1]. Studies included complete autopsies with histological examination, determination of the pancreatic content of immunoreactive insulin, and the measurement of the plasma glucose concentration. Mononuclear cell infiltrates were identified in the lung, liver, kidney, salivary gland, mesentery, and pancreas. In the latter site, the infiltrates were situated in fibrous septae about ducts, ductules, and venules rather than islets. Only islets contiguous to infiltrates were involved, and then but focally. Insulitis, as manifest by the envelopment and permeation of islets by mononuclear cells, was not observed. In none was there a significant reduction of beta cells or pancreatic insulin content, neither was hyperglycaemia manifest. This study reveals that, although NZB mice are subject to autoimmune phenomena and widespread mononuclear cell infiltrates, beta cell injury and insulitis are not consistent features of this strain.

The graft-versus-host reaction and immune function. I. T helper cell immunodeficiency associated with graft-versus-host-induced thymic epithelial cell damage

The injection of parental A strain lymphoid cells into adrenalectomized CBAxA F1 (BAF1) mice induced a chronic graft-versus-host (GVH) reaction resulting in T cell and B cell immunosuppression as well as thymic epithelial cell injury, but not stress-related thymic involution. Thymocytes from BAF1 mice undergoing a GVH reaction were studied for their ability to reconstitute T helper cell (TH) function and phytohemagglutinin (PHA) and concanavalin A (Con A) mitogen responses in thymectomized, irradiated, BAF1 mice reconstituted with normal syngeneic bone marrow (ATxBM). Thymocytes from BAF1 mice early after the induction of a GVH reaction (days 10-12) were as effective as normal thymocytes in reconstituting TH and mitogen responses. Thymocytes from BAF1 mice 40 or more days after the induction of a GVH reaction did not reconstitute either the TH function or PHA and Con A responses in ATxBM mice. The inability to reconstitute ATxBM mice was not due to the presence of suppressor cells contained in the thymocyte inoculum. It is proposed that GVH-induced thymic epithelial cell injury blocks or arrests normal T cell differentiation, resulting in a population of thymocytes that lack the potential to become competent T helper cells or mitogen-responsive cells when transferred into ATxBM mice. This thymic functional defect results in a permanent TH immunodeficiency in mice experiencing a chronic GVH reaction.