Beta transforming growth factors are potential regulators of B lymphopoiesis.

Members of the transforming growth factor beta (TGF-beta) family of polypeptides were found to be potent in vitro inhibitors of kappa light chain expression on normal bone marrow-derived and transformed cloned pre-B cells, and of the maturation of these cells to mitogen responsiveness. The inhibition by TGF-beta was selective in that Ia expression was not blocked. Together with the observations that LPS, IL-1, NZB serum factors, IL-4, and IFN-gamma preferentially induced either kappa or Ia, or both, on a pre-B cell line, these results further suggest that acquisition of Ig and class II molecules is independently controlled by different antagonists as well as agonists. In addition, kappa chain induction by IFN-gamma does not appear to be as sensitive to TGF-beta downregulation as that stimulated by other factors tested, and this raises the possibility that activation of the same gene may result from different transmembrane signaling pathways. In contrast to the inhibitory effects of TGF-beta on kappa acquisition by pre-B cells and on kappa increase after exposure of mature B cells to LPS, as measured by kappa RNA levels and/or surface fluorescence, no inhibition was observed on unstimulated spleen B cells or on two cloned B cell lines that constitutively produce kappa. Thus, TGF-beta may function during specific stages of B cell differentiation by inhibiting initiation of, or increased transcription of Ig genes, and therefore, may be an important negative regulator of B lymphopoiesis. It is the first natural substance found to have this effect.

Transforming growth factor beta 1 selectively regulates early murine hematopoietic progenitors and inhibits the growth of IL-3-dependent myeloid leukemia cell lines.

Transforming growth factor beta 1 (TGF-beta 1) has been shown to be associated with active centers of hematopoiesis and lymphopoiesis in the developing fetus. Therefore, the effects of TGF-beta 1 on mouse hematopoiesis were studied. TGF-beta 1 is a potent inhibitor of IL-3-induced bone marrow proliferation, but it does not inhibit the proliferation induced by granulocyte/macrophage, colony-stimulating factor (CSF), granulocyte CSF, and erythropoietin (Epo). TGF-beta 1 also inhibits IL-3-induced multipotential colony formation of bone marrow cells in soft agar, which includes early erythroid differentiation, while Epo-induced terminal differentiation is unaffected. In addition, IL-3-induced granulocyte/macrophage colonies were inhibited; however, small clusters of differentiated myeloid cells were consistently seen in cultures containing IL-3 and TGF-beta 1. Thus, TGF-beta 1 selectively inhibits early hematopoietic progenitor growth and differentiation but not more mature progenitors. TGF-beta 1 is also a potent inhibitor of IL-3-dependent and -independent myelomonocytic leukemic cell growth, while the more mature erythroid and macrophage leukemias are insensitive. Therefore, TGF-beta 1 functions as a selective regulator of differentiating normal hematopoietic cells, and suppresses myeloid leukemic cell growth.

Bacterial cell wall-induced immunosuppression. Role of transforming growth factor beta.

Group A streptococcal cell wall (SCW)-injected rats exhibit a profound immunosuppression that persists for months after the initial intraperitoneal injection of SCW. The goal of this study was to determine the mechanisms for the suppressed T lymphocyte proliferative responses in this experimental model of chronic inflammation. When spleen cell preparations were depleted of adherent cells, restoration of T cell proliferative responses to Con A and PHA occurred, implicating adherent macrophages in the regulation of immunosuppression. Furthermore, macrophages from SCW-treated animals, when cocultured with normal spleen cells in the presence of Con A or PHA, effectively inhibited the proliferative response. Supernatants from suppressed spleen cell cultures were found to inhibit normal T cell mitogenesis. Taken together, these results implicated a soluble macrophage-derived suppressor factor in the down regulation of T cell proliferation after exposure to SCW in vivo. Subsequent in vitro studies to identify this suppressor molecule(s) revealed the activity to be indistinguishable from the polypeptide transforming growth factor beta (TGF-beta). Furthermore, TGF-beta was identified by immunolocalization within the spleens of SCW-injected animals. The cells within the spleen that stained positively for TGF-beta were phagocytic cells that had ingested, and were presumably activated by, the SCW. These studies document that TGF-beta, previously shown to be a potent immunosuppressive agent in vitro, also effectively inhibits immune function in chronic inflammatory lesions in vivo.

Rapid onset synovial inflammation and hyperplasia induced by transforming growth factor beta.

After intraarticular injection of TGF-beta 1 or TGF-beta 2, marked swelling and erythema of the injected joints were apparent within 12-24 h. On a scale of 0 to 4, by day 3, the TGF-beta-treated joints had articular indices (AI) of 3.6 +/- 0.5 to 4.0 +/- 0.0 compared with no response for the vehicle-injected contralateral joints. Histopathologic evaluation revealed a predominantly mononuclear phagocyte infiltrate with some neutrophils and T lymphocytes, consistent with active inflammation. The monocytic pattern of leukocyte infiltration at 2-3 d was comparable to that seen in animals with antigen-induced arthritis after 2-3 wk. Extensive synovial fibroblast hyperplasia became apparent within 48 h, likely as a result of TGF-beta induction of growth factor synthesis by the accumulating monocytes. TGF-beta 2, a homologue of TGF-beta 1, was found to induce a similar level of synovitis and synovial hyperplasia consistent with its parallel monocyte and fibroblast chemotactic properties and ability to induce transcription and translation of monocyte/macrophage-derived growth factors. These data suggest that TGF-beta, released by platelets and activated inflammatory cells, may play a direct role in leukocyte recruitment and activation in arthritic and other chronic inflammatory lesions.

Macrophage- and astrocyte-derived transforming growth factor beta as a mediator of central nervous system dysfunction in acquired immune deficiency syndrome.

The multifunctional cytokine, transforming growth factor beta (TGF-beta), was identified by immunocytochemistry in the brain tissues of four patients with acquired immune deficiency syndrome (AIDS), but not in control brain tissue. The TGF-beta staining was localized to cells of monocytic lineage as well as astrocytes, especially in areas of brain pathology. In addition, the brain tissues from the AIDS patients contained transcripts for human immunodeficiency virus 1 (HIV-1) by in situ hybridization, suggesting a correlation between the presence of HIV-1 in the brain and the expression of TGF-beta. However, the expression of TGF-beta was not limited to HIV-1-positive cells, raising the possibility of alternative mechanisms for the induction of TGF-beta in these AIDS patients' brains. To investigate these mechanisms, purified human monocytes were infected in vitro with HIV-1 and were shown to secrete increased levels of TGF-beta. In addition, HIV-1-infected monocytes released a factor(s) capable of triggering cultured astrocytes that are not infected with HIV-1 to secrete TGF-beta. The release of TGF-beta, which is an extremely potent chemotactic factor, may contribute to the recruitment of HIV-1-infected monocytic cells, enabling viral spread to and within the central nervous system (CNS). Moreover, TGF-beta augments cytokine production, including cytokines known to be neurotoxic. The identification of TGF-beta within the CNS implicates this cytokine in the immunopathologic processes responsible for AIDS-related CNS dysfunction.

Expression of transforming growth factor-beta 1 in specific cells and tissues of adult and neonatal mice.

We have used immunohistochemical techniques to detect transforming growth factor-beta 1 (TGF-beta 1) in many tissues of adult and neonatal mice. Each of two antibodies raised to the amino-terminal 30 amino acids of TGF-beta 1 selectively stained this molecule in either intracellular or extracellular locations. Strong intracellular staining was found in adrenal cortex, megakaryocytes and other cells of the bone marrow, cardiac myocytes, chondrocytes, renal distal tubules, ovarian glandular cells, and chorionic cells of the placenta. Marked staining of extracellular matrix was found in cartilage, heart, pancreas, placenta, skin, and uterus. Staining was often particularly intense in specialized cells of a given tissue, suggesting unique roles for TGF-beta within that tissue. Levels of expression of mRNA for TGF-beta 1 and its histochemical staining did not necessarily correlate in a given tissue, as in the spleen. The present data lend further support to the concept that TGF-beta has an important role in controlling interactions between epithelia and surrounding mesenchyme.

Transforming growth factor-beta 1: histochemical localization with antibodies to different epitopes.

We have localized transforming growth factor-beta (TGF-beta) in many cells and tissues with immunohistochemical methods, using two polyclonal antisera raised to different synthetic preparations of a peptide corresponding to the amino-terminal 30 amino acids of TGF-beta 1. These two antibodies give distinct staining patterns; the staining by anti-CC(1-30) is intracellular. This differential staining pattern is consistently observed in several systems, including cultured tumor cells; mouse embryonic, neonatal, and adult tissues; bovine fibropapillomas; and human colon carcinomas. The extracellular staining by anti-CC(1-30) partially resembles that seen with an antibody to fibronectin, suggesting that extracellular TGF-beta may be bound to matrix proteins. The intracellular staining by anti-LC(1-30) is similar to that seen with two other antibodies raised to peptides corresponding to either amino acids 266-278 of the TGF-beta 1 precursor sequence or to amino acids 50-75 of mature TGF-beta 1, suggesting that anti-LC(1-30) stains sites of TGF-beta synthesis. Results from RIA and ELISAs indicate that anti-LC(1-30) and anti-CC(1-30) recognize different epitopes of this peptide and of TGF-beta 1 itself.

Role of transforming growth factor-beta in the development of the mouse embryo.

Using immunohistochemical methods, we have investigated the role of transforming growth factor-beta (TGF-beta) in the development of the mouse embryo. For detection of TGF-beta in 11-18-d-old embryos, we have used a polyclonal antibody specific for TGF-beta type 1 and the peroxidase-antiperoxidase technique. Staining of TGF-beta is closely associated with mesenchyme per se or with tissues derived from mesenchyme, such as connective tissue, cartilage, and bone. TGF-beta is conspicuous in tissues derived from neural crest mesenchyme, such as the palate, larynx, facial mesenchyme, nasal sinuses, meninges, and teeth. Staining of all of these tissues is greatest during periods of morphogenesis. In many instances, intense staining is seen in mesenchyme when critical interactions with adjacent epithelium occur, as in the development of hair follicles, teeth, and the submandibular gland. Marked staining is also seen when remodeling of mesenchyme or mesoderm occurs, as during formation of digits from limb buds, formation of the palate, and formation of the heart valves. The presence of TGF-beta is often coupled with pronounced angiogenic activity. The histochemical results are discussed in terms of the known biochemical actions of TGF-beta, especially its ability to control both synthesis and degradation of both structural and adhesion molecules of the extracellular matrix.

Transforming growth factor-beta in leishmanial infection: a parasite escape mechanism.

The course of infection with the protozoan parasite Leishmania is determined in part by their early replication in macrophages, the exclusive host cells for these organisms. Although factors contributing to the survival of Leishmania are not well understood, cytokines influence the course of infection. Transforming growth factor-beta (TGF-beta) is a multipotential cytokine with diverse effects on cells of the immune system, including down-regulation of certain macrophage functions. Leishmanial infection induced the production of active TGF-beta, both in vitro and in vivo. TGF-beta was important for determining in vivo susceptibility to experimental leishmanial infection.

Overexpression of transforming growth factor alpha in psoriatic epidermis.

Transforming growth factor alpha (TGF-alpha) is produced by and required for the growth of epithelial cells and is angiogenic in vivo. Since epidermal hyperplasia and angiogenesis are hallmarks of psoriasis, TGF-alpha gene expression was analyzed in epidermal biopsies of normal and psoriatic skin. TGF-alpha messenger RNA and protein are much more abundant in lesional psoriatic epidermis than in normal-appearing skin of psoriatic patients or in normal epidermis. In contrast, messenger RNA levels of transforming growth factor beta 1 (TGF-beta 1), which inhibits epithelial cell growth, are not significantly different in normal, uninvolved, and lesional psoriatic epidermis. Thus, psoriatic epidermal hyperplasia may involve increased expression of a keratinocyte mitogen (TGF-alpha) rather than deficient expression of a growth inhibitor (TGF-beta 1).

Response of bone marrow stromal cells to adipogenic antagonists.

Adipocytes constitute a major part of the bone marrow stroma in vivo and may play an active role in lymphohematopoiesis. Earlier studies had shown that the bone marrow stromal cell clone BMS2 was capable of adipocyte differentiation in vitro, in addition to its well-defined ability to support B lymphopoiesis. We now demonstrate that the process of adipogenesis in this functional bone marrow stromal cell clone can be inhibited by the cytokines interleukin-1 alpha, tumor necrosis factor, and transforming growth factor beta. Exposure of preadipocyte BMS2 cells to these agents blocked the induction of adipocyte differentiation as assessed by morphologic criteria and analysis of the neutral lipid content. Both interleukin-1 alpha and tumor necrosis factor elicited a rapid transient elevation in the steady-state mRNA levels of c-fos, c-jun, and JE. When added to differentiated adipocytes, the three cytokines continued to act as adipogenic antagonists. This was indicated by concentration- and time-dependent decreases in the activity of an adipocyte-specific enzyme, lipoprotein lipase. These changes in enzyme activity correlated directly with a decrease in steady-state levels of lipoprotein lipase mRNA. Another RNA marker of adipocyte differentiation (adipsin) was less influenced by the adipogenic antagonists. This may reflect the longer half-life of this mRNA transcript compared with those of lipoprotein lipase. Our results dramatically demonstrate that the differentiation state of bone marrow stromal cells can be modulated by exogenous factors in vitro. It is also the first report that transformation growth factor beta regulates the activity of lipoprotein lipase. These data suggest potential physiologic actions for these cytokines in vivo within the overall context of lymphohematopoiesis.

The suppressive effects of type beta transforming growth factor (TGF beta) on primitive murine hemopoietic progenitors are abrogated by interleukin-6 and granulocyte colony-stimulating factor.

We examined the effects of type beta transforming growth factor (TGF beta) on colony formation by murine hemopoietic progenitors in methylcellulose culture. TGF beta inhibited colony formation from spleen cells of normal mice supported by interleukin-3 (IL-3) and erythropoietin (Ep). The suppressive effects of TGF beta were more profound on colony formation from cells of 5-fluorouracil (5-FU)-treated mice than those of normal mice. Addition of IL-6 or granulocyte colony-stimulating factor (G-CSF), which act synergistically with IL-3 on dormant progenitors, partially neutralized the inhibition by TGF beta of colony formation from cells of 5-FU-treated mice. We then exposed day-2 post-5-FU marrow cells to these factors for 2 days in serum-free suspension culture, washed, and replated alliquots of cells for analysis of the surviving fractions of the progenitors. While TGF beta almost totally abolished the colony-forming ability of the dormant progenitors, IL-6 and G-CSF abrogated the inhibitory effects of TGF beta. These results indicated that TGF beta and early-acting hemopoietic factors (IL-6 and G-CSF) possess counteracting effects on early progenitors.

Transforming growth factor beta 1 systemically modulates granuloid, erythroid, lymphoid, and thrombocytic cells in mice.

Transforming growth factor beta 1 (TGF-beta 1) has been shown to inhibit the development of most early hemopoietic progenitors in vitro. The present series of in vivo experiments show that TGF-beta 1 can simultaneously augment and suppress distinct cell lineages in peripheral and central hemopoietic compartments. Mice treated daily for 7-14 days with s.c. injections of TGF-beta 1 exhibited up to a 95% reduction in circulating platelets and a 50% reduction in red cell counts, whereas a 50%-400% increase occurred in circulating white cells with the morphology of small lymphocytes. Decreased erythrocytes were also evident in the splenic red pulp and bone marrow sinusoids. A dramatic increase in granulopoiesis occurred in the spleen and bone marrow, followed by a peripheral neutrophilia 1 week after treatments ceased. All effects were completely reversible, with normal histologic and hematologic profiles evident 2 weeks after cessation of treatments. Thus, TGF-beta 1 can differentially regulate multiple hemopoietic pathways in a systemic, reversible, and dose-dependent fashion. These actions may be mediated by the direct effects of TGF-beta 1 or through modulation of secondary cytokines and receptors.

Differential modulation of transforming growth factor-beta 1 expression and mucin deposition by retinoic acid and sodium lauryl sulfate in human skin.

Immunohistochemical staining of skin sections with two polyclonal antibodies (anti-CC 1-30 and anti-LC 1-30), specific for transforming growth factor-beta 1, revealed increased extracellular and decreased intracellular expression of transforming growth factor-beta 1 in retinoic acid-treated, compared to vehicle-treated, skin. Transforming growth factor-beta 1 staining, with both antibodies, was most marked in the upper layers of the epidermis, although dermal staining was also evident. The modulation of transforming growth factor-beta 1 expression by retinoic acid occurred in the absence of any change in its mRNA level. Transforming growth factor-beta 1 protein, as detected by rabbit polyclonal antibody (anti-LC 50-75) and mRNA, were only minimally detected in either retinoic acid- or vehicle-treated skin. Similar changes in TGF-beta 1 and TGF-beta 2 immunoreactivity and mRNA levels, as observed in retinoic acid-treated skin, were observed in skin following topical application of the irritant sodium lauryl sulfate, indicating that the alterations induced by retinoic acid were not specific. In contrast, mucin deposition, which is induced by transforming growth factor-beta, was elevated in retinoic acid-treated but not sodium lauryl sulfate-treated skin. Cultured adult human keratinocytes also expressed predominantly transforming growth factor-beta 1 protein, as measured by ELISA, and mRNA. Treatment of keratinocytes with retinoic acid resulted in a 50% induction of transforming growth factor-beta 1 protein, without any detectable change in transforming growth factor-beta 2. These data demonstrate disassociation of modulation of transforming growth factor-beta 1 expression and mucin deposition by retinoic acid and sodium lauryl sulfate in human skin in vivo. Whereas alterations in transforming growth factor-beta 1 expression were observed in both retinoic acid- and sodium lauryl sulfate-treated skin, accumulation of mucin was specific to retinoic acid-treated skin.

A novel polyclonal antibody (CL-B1/29) for immunolocalization of transforming growth factor-beta 2 (TGF-beta 2) in adult mouse.

A polyclonal antibody (CL-B1/29) raised against a synthetic peptide with an amino acid sequence identical to the first 29 N-terminal residues of bovine bone-derived transforming growth factor-beta 2 (TGF-beta 2) was characterized and used for immunolocalization of TGF-beta 2 in adult mice. Reduced staining of immunoblots and tissue after absorption of the antiserum with the immunizing peptide or with TGF-beta 2 but not with purified TGF-beta 1 demonstrated that the reagent is specific for TGF-beta 2, with little or no crossreactivity with TGF-beta 1. The immunolocalization of TGF-beta 2 was investigated in formalin-fixed, paraffin-embedded cultured cells and murine tissue. Specimens pre-digested with testicular hyaluronidase demonstrated immunostaining predominantly of extracellular connective tissue matrix, whereas specimens pre-digested with pronase E demonstrated primarily cytoplasmic staining. Immunoreactivity was widely distributed in connective tissue, muscle, adsorptive and secretory epithelia, especially of endocrine tissue, and neural tissue of adult mice.

Osteogenesis in rats with an inductive bovine composite.

Subcutaneous (S.C.) implantation of allogeneic demineralized bone matrix in rats results in endochondral bone formation. In contrast, implants of bovine demineralized bone matrix in rat S.C. tissue show inconsistent cartilage and bone formation, presumably due to an intense inflammatory reaction at the implant site. To overcome this response, a partially purified bone inducing extract was prepared from bovine bone by a series of steps that included demineralization, guanidine/HCl extraction, gel filtration, and cation exchange chromatography. To develop a carrier, the inactive guanidine/HCl-extracted matrix was then trypsinized to remove the inflammatory and immunogenic components, thus yielding a predominantly collagenous matrix. Bovine composites were prepared by combining different amounts of the bone inducing extract with a carrier that consisted of the trypsinized bone matrix and purified soluble bovine dermal collagen. Subcutaneous implantation of the composite preparation resulted in dose-dependent endochondral bone formation in rats. The inductive activity and the low-level inflammatory response were comparable to allogeneic implants.

Hemolytic complement measurement in eleven species of nonhuman primates.

A microtiter system was used to measure hemolytic complement levels in serum from eleven nonhuman primate species. The species studied were Macaca mulatta (rhesus macaque), Macaca radiata (bonnet macaque), Macaca nemestrina (pig-tailed macaque), Macaca fascicularis (crab-eating macaque), Macaca speciosa (stumptailed macaque), Papio cynocephalus (yellow baboon), Papio anubis (olive baboon), Cercopithecus aethiops (African green monkey), Aotus trivirgatus (owl monkey), Ateles fusceps robustus (spider monkey), and Galago crassicaudatus panganiensis (thick-tailed galago). The optimal hemolytic complement titer of the various nonhuman primate species was found to vary with different species sources of erythrocytes and anti-erythrocyte reagents used in the assay. No single erythrocyte and anti-erythrocyte test reagent produced optimal titers for all of the primate species examined. Sera from several species was found to have high spontaneous lytic activity towards non-sensitized sheep erythrocytes which for six species (M. mulatta, M. radiata, M. speciosa, P. cynocephalus, P. anubis and A. trivirgatus) was equal to the titer for antibody sensitized erythrocytes. Evidence of alternate pathway complement activation as a possible reason for the high titer of lytic activity towards unsensitized erythrocytes could not be demonstrated for any nonhuman primate species. In one species, M. mulatta, the sensitizing activity of normal serum for sheep erythrocytes was shown to be in the IgM containing fraction obtained with gel filtration and to be absorbed by boiled sheep erythrocyte stroma which contains Forssman antigen.

Characterization of rhesus macaque peripheral blood T-lymphocyte subpopulations.

Highly enriched rhesus macaque (Macaca mulatta) peripheral blood T-lymphocytes were separated into functional subpopulations by Fc-receptors. The T-lymphocyte population was comprised of both Fc-IgM (T mu +, 3.4 +/- 1.6) and Fc-IgG (T gamma +, 16.2 +/- 4.0) bearing cells. T-cells depleted of cells bearing Fc-IgG receptors (T gamma -) and T gamma + subpopulations were characterized and assessed for functional activity. T gamma + and T gamma - subpopulations were found to have the following characteristics: 1) T gamma + cells were stimulated by concanavalin-A (Con-A)3, pokeweed mitogen (PWM), and phytohemagglutinin-P (PHA-P), while T gamma - cells were stimulated by Con-A and PWM, but not PHA-P; 2) T gamma - cells were found to mediate PWM induced differentiation of autologous B-cells including EAC+ and EAC- enriched subpopulations, while T gamma + cells did not induce differentiation; 3) T gamma + cells released soluble factors which depressed mitogen stimulation of T gamma- cells; and 4) approximately 8-10% of the T gamma + cells phagocytized IgG sensitized bovine red blood cell (BRBC) immune complexes.

Reaction to injectable collagen: results in animal models and clinical use.

Since its commercial release, Zyderm collagen implant has been used to treat more than 200,000 subjects in the United States for soft-tissue contour defects and more than 250,000 patients internationally (including the United States). Approximately 3 percent of subjects' skin tested with Zyderm collagen experience localized hypersensitivity reactions to collagen, whereas approximately 1 percent of treated patients demonstrate symptoms of hypersensitivity at treatment sites. Of the latter treatment responses reported since the conclusion of clinical trials with Zyderm, 56 percent occurred following the first treatment, 28 percent following the second, 10 percent following the third, and 6 percent following subsequent exposures. The data indicate that most patients receive a median of three treatments (mean = 4.4) with Zyderm collagen, but most patients who are likely to develop sensitivity to Zyderm collagen appear to respond immunologically to the test implant or first treatment exposure. Examining these treatment responses, 45 percent of the patients reported an onset of symptoms within 10 days and 22 percent at more than 30 days following the last treatment with Zyderm collagen. Erythema was the sole symptom in 24 percent of cases, whereas erythema plus induration comprised an additional 42 percent. Antibodies against Zyderm collagen were detected in the sera of 88 percent of these subjects using an ELISA, but no reactivity was observed against human collagen. Sera from patients reporting only systemic symptoms were not found to have anticollagen antibodies. These data suggest that the relative risk of a hypersensitivity reaction to Zyderm collagen does not increase with multiple exposures, since patients who are going to develop an immune response to bovine collagen react with greatest frequency to initial injections of collagen. In animal models, Zyderm collagen was shown to be less immunogenic than other medical devices which are composed of bovine collagen. Specifically, comparative studies were conducted in which Zyderm collagen and hemostatic agents were implanted in the guinea pig subcutaneum: sera from animals treated with collagen-derived hemostatic devices possessed significant levels of anti-implant antibodies (titers greater than 640), whereas animals treated with Zyderm collagen mounted minimal responses (titers less than 40). Additional studies were conducted in which implant materials were compared in a guinea pig parietal (bony defect) model and in a rabbit hemostasis model: in both, Zyderm collagen demonstrated lower immunogenicity than commercial bovine collagen hemostatic agents. Histologic results from these studies showed Zyderm

Immunologic abnormality in a group of Macaca arctoides with high mortality due to atypical mycobacterial and other disease processes.

Of 54 Macaca arctoides, 44 died during the 2.5 years after their assignment to a common cage. Although early deaths were due to trauma, acute gastric dilatation, and shigellosis; latter deaths were the result of a variety of uncommon diseases including atypical mycobacterial disease, malignant lymphoma, protozoan encephalomyelitis, and other necrotizing and inflammatory lesions. Atypical mycobacterial disease due to Mycobacterium avium intracellular serotypes was the most frequent single disease agent recognized (33% [18 macaques]). This disease began in the ileum and large intestine with subsequent systemic involvement. An abnormality of host response to infective agents, in general, was indicated by the unusually high occurrence of this disease, as well as other disease processes. Morphologic evaluation of lymphoid organs revealed decreased cellularity of follicles and decreased numbers of plasma cells in all macaques, whereas T cell-dependent areas varied from hypocellular to hypercellular with 5 macaques with malignant lymphoma. The spontaneous erythrocyte rosette-forming subpopulation of T cells was decreased in peripheral blood, but was increased in lymph nodes containing atypical mycobacterial lesions. Serum immunoglobulin value decreased progressively in diseased macaques. A basic abnormality of T-cell subpopulations controlling other components of host response was suspected. Macrophages from lesions that contain mycobacterial organisms did not phagocytize latex beads normally in vitro, whereas monocytes in the blood of the same macaques were capable of in vitro phagocytosis.