Vaccine safety--vaccine benefits: science and the public's perception.

The development of cowpox vaccination by Jenner led to the development of immunology as a scientific discipline. The subsequent eradication of smallpox and the remarkable effects of other vaccines are among the most important contributions of biomedical science to human health. Today, the need for new vaccines has never been greater. However, in developed countries, the public's fear of vaccine-preventable diseases has waned, and awareness of potential adverse effects has increased, which is threatening vaccine acceptance. To further the control of disease by vaccination, we must develop safe and effective new vaccines to combat infectious diseases, and address the public's concerns.

Long-term hepatic adenovirus-mediated gene expression in mice following CTLA4Ig administration.

Recombinant adenovirus vectors are efficient at transferring genes into somatic tissues but are limited for use in clinical gene therapy by immunologic factors that result in the rapid loss of gene expression and inhibit secondary gene transfer. This study demonstrates that systemic coadministration of recombinant adenovirus with soluble CTLA4Ig, which is known to block co-stimulatory signals between T cells and antigen presenting cells, leads to persistent adenoviral gene expression in mice without long-term immunosuppression. This form of immunotherapy greatly enhances the likelihood that recombinant adenovirus vectors will be useful for human gene therapy.

A randomised study evaluating the use of pyridoxine to avoid capecitabine dose modifications.

BACKGROUND: Pyridoxine is frequently used to treat capecitabine-induced hand-foot syndrome (HFS), although the evidence of benefit is lacking. We performed a randomised placebo-controlled trial to determine whether pyridoxine could avoid the need for capecitabine dose modifications and improve outcomes. METHODS: A total of 106 patients planned for palliative single-agent capecitabine (53 in each arm, 65%/35% colorectal/breast cancer) were randomised to receive either concomitant pyridoxine (50 mg po) or matching placebo three times daily. RESULTS: Compared with placebo, pyridoxine use was associated with an increased rate of avoiding capecitabine dose modifications (37% vs 23%, relative risk 0.59, 95% CI 0.29, 1.20, P=0.15) and fewer grade 3/4 HFS-related adverse events (9% vs 17%, odds ratio 0.51, 95% CI 0.15-1.6, P=0.26). Use of pyridoxine did not improve response rate or progression-free survival. CONCLUSION: Pyridoxine may reduce the need for capecitabine dose modifications and the incidence of severe HFS, but does not impact on antitumour effect.

Reduced interferon-gamma mRNA levels in human neonates. Evidence for an intrinsic T cell deficiency independent of other genes involved in T cell activation.

IFN-gamma mRNA levels in human neonatal blood mononuclear cells or highly purified T cells were markedly lower than those of adult cells after incubation with Con A and PMA. In contrast, IL-2, IL-2-R, and T3 delta chain mRNA levels were kinetically and quantitatively similar in neonatal and adult T cells. The peak amount of IFN-gamma and IL-2 mRNA correlated well with IFN-gamma and IL-2 detected in supernatants of both neonatal and adult T cells. These results suggest that reduced IFN-gamma mRNA levels in neonatal T cells is due to an intrinsic deficiency at the pretranslational level and indicate that the magnitude of IL-2 and IFN-gamma gene expression can be independently modulated pretranslationally.

Quantitation of acute and chronic serum sickness in the rabbit.

The amounts of BSA (immune complex) deposited in glomeruli of rabbits with acute and chronic serum sickness were determined using radio-labeled BSA and paired-label RSA. In animals with acute serum sickness and severe glomerulonephritis, about 18 microg of I*BSA were present in both kidneys after immune elimination (>99% of the circulating I*BSA). Visible with an immunofluorescent sensitivity of 0.25 microg per g of kidney, the I*BSA became rapidly undetectable and was presumably covered by deposits of circulating host anti-BSA and complement which increased demonstrably. In chronic serum sickness produced by daily injections of a quantity of BSA to balance antibody production, 0.04% of the daily dose of I*BSA was deposited in the glomeruli during the developmental stages of glomerulonephritis. Coincident with the onset of overt proteinuric glomerulonephritis, the daily I*BSA deposition, rate increased to about 0.5% of the daily dose. The half-disappearance rate of I*BSA from the kidney was about 5 days. Administration of huge excesses of BSA caused a fivefold increase in the half-disappearance rate. The accelerated I*BSA disappearance could be correlated with vanishing glomerular immunofluorescent deposits of BSA and immunoglobulin, as well as electron microscopic dense deposits; however, functional improvement of the disease was not observed. The roles of immune complex size, precipitating and nonprecipitating (total ABC) antibodies, and RES function in the development of chronic serum sickness glomerulonephritis are discussed.

Failure to trigger the oxidative metabolic burst by normal macrophages: possible mechanism for survival of intracellular pathogens.

As previously reported, normal human monocytes (11) and activated mouse macrophages (9) are able to kill or inhibit intracellular replication of Toxoplasma that are not antibody coated, whereas normal human and mouse macrophages are not (7, 9). Each of these types of mononuclear phagocytes is able to kill antibody-coated Toxoplasma. In our studies, phagocytosis of antibody-coated Toxoplasma stimulated the respiratory burst by each of these types of mononuclear phagocytes, whereas phagocytosis of organisms that were not antibody coated stimulated the respiratory burst only by human monocytes and by activated mouse macrophages. Phagocytosis of Toxoplasma did not inhibit production of reactive oxygen metabolites by normal macrophages; rather, it failed to stimulate their production. Killing of Toxoplasma by monocytes from a child with X-linked chronic granulomatous disease and his heterozygote mother was impaired. Thus, reactive oxygen metabolites, perhaps in conjunction with lysosomal contents, appear to be first-line mechanisms whereby mononuclear phagocytes kill this organism. We were not able to determine the exact mechanisms whereby mononuclear phagocytes inhibit the replication of those Toxoplasma that were not killed, although both oxygen-dependent and other nonlysosomal mechanisms may be involved. The differences we observed in oxidative response to phagocytosis of Toxoplasma appear to be one determinant of the antimicrobial activity of these cells and may account for the ability of some intracellular pathogens to survive within phagocytes. These differences may be membrane related. Further studies of Toxoplasma membranes, phagocyte membrane receptors for Toxoplasma, and membrane-related mechanisms for activation of the respiratory burst are needed to define their true basis.

Augmented expression of a myeloid-specific protein tyrosine kinase gene (hck) after macrophage activation.

Protein tyrosine kinases are thought to participate in signal transduction pathways in a variety of cell types. Recent studies have identified a new src family protein tyrosine kinase (hck) that is preferentially expressed in myeloid cells. To examine the hypothesis that this kinase may regulate myeloid cell activity, antisera were generated that define the 59-kD product of the hck gene. Functional activation of human cultured macrophages with LPS augmented the expression of hck transcripts and of p59hck, but decreased the level of transcripts encoded by the closely related c-fgr protooncogene. Thus these two structurally similar src family kinases almost certainly subserve distinct functions. Reasoning from the known properties of the src family protein tyrosine kinases, it is likely that the products of these two protooncogenes assist in regulating the behavior of activated phagocytes.

Thymus-dependent lymphocytes in tissue sections of rejecting rat renal allografts.

Lewis kidneys were grafted into BN recipients and examined at daily intervals up to 6 days after grafting with immunofluorescent reagents. A horse antiserum specific for T lymphocytes revealed an increasing number of T lymphocytes in the cellular infiltrates of rejecting allografts. These were detectable 1 day after grafting, reached a maximum 3 days later, and were relatively diminished at 6 days. In control isografts and nonimmunological inflammations of kidney, a small number of dispersed T lymphocytes was seen. A rabbit antirat thymocyte antiserum, given to allografted BN rats, prolonged survival of the grafts and decreased the cellular infiltrate and the number of T lymphocytes in the infiltrates. We conclude that in graft rejection there is a flow of T lymphocytes into areas of tissue damage and these T lymphocytes are immunologically reactive to graft antigens.

Interstitial immune complex thyroiditis in mice: the role of autoantibody to thyroglobulin.

Mice immunized with soluble heterologous thyroglobulins developed autoantibody that cross-reacted with autologous thyroglobulin. There was a direct correlation between the temporal appearance and quantity of serum autoantibody and the presumed in situ formation of immune complexes in the interstitium of the thyroid glands. Immediately after the formation of interstitial immune complexes containing antibody of the IgG complement-fixing type, the thyroids were invaded by a transient but intense neutrophil infiltrate which within 1 wk was replaced by chronic mononuclear elements. By the combination of fluorescence microscopy and autoradiography, thyroglobulin was demonstrated to be one, if not the sole, antigen in the interstitial immune complexes. The interstitial immune complexes were granular to lumpy in appearance and formed at the basal area of the follicular cells in intimate association with the follicular basement membrane. Electron microscopy revealed electron dense deposits, presumably immune complexes, between the follicular basement membrane and the plasma membrane. The presumed in situ formation of immune complexes in this model is similar to that which occurs in the Arthus reaction and is a different mechanism of immune complex injury than that caused by tissue deposition of circulating immune complexes as occurs in serum sickness.

Two essential regulatory elements in the human interferon gamma promoter confer activation specific expression in T cells.

Like interleukin 2 (IL-2), interferon gamma (IFN-gamma) is an early response gene in T cells and both are prototypical T helper cell type 1 (Th-1) lymphokines. Yet IL-2 and IFN-gamma production are independently regulated, as demonstrated by their differential expression in certain T cell subsets, suggesting that the regulatory elements in these two genes must differ. To explore this possibility, the 5' flank of the human IFN-gamma gene was analyzed. Expression of IFN-gamma promoter-driven beta-galactosidase reporter constructs containing 538 bp of 5' flank was similar to that by constructs driven by the IL-2 promoter in activated Jurkat T cells; expression nearly as great was observed with the construct containing only 108 bp of IFN-gamma 5' flank. These IFN-gamma promoter constructs faithfully mirrored expression of the endogenous gene, in that expression required activation both with ionomycin and PMA, was inhibited by cyclosporin A, and was not observed in U937 or THP-1 cells. The region between -108 and -40 bp in the IFN-gamma promoter was required for promoter function and contained two elements that are conserved across species. Deletion of 10 bp within either element reduced promoter function by 70%, whereas deletions in nonconserved portions of this region had little effect on promoter function. The distal conserved element (-96 to -80 bp) contained a consensus GATA motif and a potential regulatory motif found in the promoter regions of the GM-CSF and macrophage inflammatory protein (MIP) genes. Factors binding to this element, including GATA-3, were found in Jurkat nuclear extracts by electromobility shift assays and two of the three complexes observed were altered in response to activation. One or both of these motifs are present in the 5' flank of multiple, other lymphokine genes, including IL-3, IL-4, IL-5, and GM-CSF, but neither is present in the promoter of the IL-2 gene. The proximal conserved element (-73 to -48 bp) shares homology with the NFIL-2A element in the IL-2 promoter; these elements compete for binding of factors in Jurkat nuclear extracts, although the NFIL-2A element but not the IFN-gamma element binds Oct-1. Factors binding to this element in the IFN-gamma gene were present in extracts from resting and activated Jurkat T cells. However, by in vivo footprinting of intact cells, this element was protected from methylation only with activation.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding of soluble immune complexes to human lymphoblastoid cells. II. Use of Raji cells to detect circulating immune complexes in animal and human sera.

Cells from a human lymphoblastoid cell line (Raji), with B-cell characteristics, and having receptors for human IgG Fc, C3b, and C3d, were used in an immunofluorescence test as in vitro detectors of immune complexes in animal and human sera. By this test, as little as 200-300 ng aggregated human gamma globulin or immune complexes per ml serum could be detected. The receptors for IgG Fc on the Raji cells were shown to be inefficient in detecting aggregated human gamma globulin and binding of aggregates to these receptors was inhibited by physiologic concentrations of 7S human IgG. Enhancement of aggregated human gamma globulin binding and binding of immune complexes formed in vitro to Raji cells was observed when the receptors for complement on these cells were used. By using the receptors for complement on Raji cells, circulating immune complexes were detected in rabbits with acute serum sickness, in mice with acute lymphocytic choriomeningitis virus infection, and in humans with immune complex type glomerulonephritis. The Raji cell test may be useful in detecting complement fixing immune complexes in different disease states, in monitoring circulating complexes in patients with immune complex diseases and in identifying the antigen(s) responsible for the induction of pathogenic immune complexes in humans and animals.

Endogenous oncornaviral gene expression in adult and fetal mice: quantitative, histologic, and physiologic studies of the major viral glycorprotein, gp70.

Endogenous expression of the murine leukemia virus (MuLV) genome has been studied in a number of strains of mice. Expression of the major envelope glycoprotein, gp70, is restricted to certain anatomical sites and cell types, prominent among which are lymphoid and epithelial cells. On a quantitative basis, the major site of gp70 expression is the male genital tract. During development, gp70 first appears in the hematopoietic liver of 14-day-old embryos and by day 18, it is already expressed at anatomical sites similar to those of the adult. In toto, these results show that control of expression of the MuLV genome in adult and developing mice is linked to differentiation.

Spontaneous murine lupus-like syndromes. Clinical and immunopathological manifestations in several strains.

MRL/1 and BXSB male mice have a systemic lupus erythematosus (SLE)-like disease similar to but more acute than that occurring in NZB X W mice. The common elements of lymphoid hyperplasia, B-cell hyperactivity, autoantibodies, circulating immune complex (IC), complement consumption, IC glomerulonephritis with gp70 deposition, and thymic atrophy were found in all three kinds of SLE mice. On the basis of these common elements, SLE seen in these mice can be considered a single disease in the same sense that human SLE is one disease. The differences in the SLE expressed in the different mice are no greater than those found in an unselected series of humans with SLE. However, the significant quantitative and qualitative variations in abnormal immunologic expression suggest that different constellations of factors, genetic and/or pathophysiologic, may operate in the three murine strains and that each constellation is capable of leading, via its particular abnormal immunologic consequences, to the activation of common immunopathologic effector mechanisms that cause quite similar SLE-like syndromes. From an experimental point of view, the availability of several inbred murine strains of commonplace histocompatibility types that express an SLE-like syndrome makes possible innumerable manipulations which should help to elucidate the nature and cause(s) of this disorder.

Cushing's syndrome: problems in management.

CS comprises a group of disorders characterized by hypercortisolism. The variety of causes--pituitary-dependent CS (CD), adrenal tumor, and the ectopic ACTH syndrome--necessitates a variety of therapies--surgical, radiotherapeutic, and medical. Once a specific diagnosis is made, specific therapy can be instituted. Although some controversy persists regarding treatment, particularly that of CD, for most patients it is straightforward. However, in our experience with more than 60 patients, therapeutic dilemmas can arise in a number of circumstances, e.g. the patient with the radiologically normal sella or recurrent CD after adrenalectomy. In addition, the treatment of such conditions as the large ACTH-producing pituitary tumor, Nelson's syndrome, the malignant ectopic ACTH syndrome, and adrenal carcinoma is not entirely satisfactory. Our approach to these problems is illustrated by seven cases, and we emphasize that the proper management of CS requires both correct diagnosis and the logical application of all available therapies.

Acute effects of antiglomerular basement membrane antibody on the process of glomerular filtration in the rat.

Nehron filtration rate (sngfr) and the factors controlling filtration were examined before and with 60 min of the intravenous infusion of 225-450 mug of antiglomerular basement membrane antibody (AGBM Ab) (greater than 50% antigenic saturation) in plasma-expanded (2.5% body wt) Munich-Wistar rats. Pressures in glomerular capillaries (PG) and bowman's space (Pt) were measured with a servo-nulling device, systemic (piA) and efferent arteriolar oncotic pressures (piE) were measured by microprotein methods, and nephron plasma flow (rpf) and sngfr were measured by micropuncture techniques in both control and post-AGBM Ab conditions in each rat. The sngfr fell from 52.7+/-2.9 to 24.1+/-1.9 nl/min per g kidney wt (n = 7, P less than 0.001). Both afferent and efferent arteriolar resistances increased and rpf fell from 221+/-25 to 90+/-9 nl/min per g kidney wt (P less than 0.001) but the hydrostatic pressure gradient across the glomerular membrane deltaP = PG - Pt) increased from 37+/- 1 to 50+/-2 mm Hg (P less than 0.001). The increase in deltaP and a numerical decrease in piA both acted to maintain sngfr after AGBM Ab and effectively nullified the influence of decreased rpf upon sngfr. The mean effective filtration pressure (EFP = deltaP - pi) increased from 14+/-2 to 30+/-3 mm Hg (P less than 0.001) while sngfr decreased. The major and critical reason for this reduction in sngfr was a decrease in the glomerular permeability coefficient from 0.077+/-0.017 to 0.014+/-0.001 nl/s per g kidney wt per mm Hg P less than 0.001) where sngfr=EFP-LpA.

Cellular defenses against Toxoplasma gondii in newborns.

Mononuclear phagocytes, particularly macrophages (M phi) that have been activated by lymphokines, are the principal defense against intracellular pathogens such as Toxoplasma gondii. To determine reasons for the newborns' susceptibility to Toxoplasma infection, we compared: the interaction of Toxoplasma with newborns' mononuclear phagocytes (blood monocytes and two types of newborn M phi, those derived from blood monocytes or from placental tissue) with adults' blood monocytes and monocyte-derived M phi and the production of M phi-activating lymphokines (MAF) by Concanavalin A (ConA)-stimulated newborn and adult blood mononuclear cells (MC). Newborn and adult monocytes killed Toxoplasma with equal efficiency. Similarly, survival and replication of Toxoplasma were comparable in control newborn and adult M phi. Exposure to adult ConA supernatants significantly decreased the survival and replication of Toxoplasma both in adult and newborn M phi. In contrast, exposure to cord blood ConA supernatants failed to affect the survival or the replication of Toxoplasma in newborn M phi and decreased the replication but not the survival of Toxoplasma in adult M phi. Exposure to ConA supernatants of peripheral blood MC from 2-5-d old newborns failed to affect survival or replication of Toxoplasma in newborn or adult M phi. Thus, both generation of MAF by newborn blood MC and response to newborn MAF by newborn M phi were impaired. Generation of MAF by adult blood mononuclear cells was not inhibited by cord blood MC nor was generation of MAF by cord blood MC increased by depletion of OKT8 antibody-binding cells, by depletion of adherent cells with or without addition of adult adherent cells, or by addition of indomethacin. Depletion of OKT4 antibody-binding cells abrogated the generation of MAF both by adult and cord blood MC. The activity of adult ConA supernatants was abrogated by dialysis at pH 2 or by addition of anti-gamma-interferon but not anti-alpha-interferon antibody. However, the correlation between antiviral interferon activity and anti-Toxoplasma activity was weak (r = 0.40). Enhanced M phi anti-Toxoplasma activity was not associated with detectably enhanced superoxide anion generation, nitroblue tetrazolium reduction, or phagolysosome fusion, and was not inhibited by catalase, superoxide dismutase, or mannitol. These results indicate that generation of and response to MAF is decreased in cells from human newborns and that gamma-interferon may be the major MAF under these conditions.

Modulation of neutrophil influx in glomerulonephritis in the rat with anti-macrophage inflammatory protein-2 (MIP-2) antibody.

The role of the chemokine, macrophage inflammatory protein-2 (MIP-2), during anti-glomerular basement membrane (GBM) antibody (Ab) glomerulonephritis (GN) was studied. Rat MIP-2 cDNA had been cloned previously. Recombinant rat MIP-2 (rMIP-2) from Escherichia coli exhibited neutrophil chemotactic activity and produced neutrophil influx when injected into the rat bladder wall. By using a riboprobe derived from the cDNA and an anti-rMIP-2 polyclonal Ab, MIP-2 was found to be induced in glomeruli with anti-GBM Ab GN as mRNA by 30 min and protein by 4 h, with both disappearing by 24 h. The expression of MIP-2 correlated with glomerular neutrophil influx. A single dose of the anti-MIP-2 Ab 30 min before anti-GBM Ab was effective in reducing neutrophil influx (40% at 4 h, P < 0.01) and periodic acid-Schiff deposits containing fibrin (54% at 24 h, P < 0.01). The anti-rMIP-2 Ab had no effect on anti-GBM Ab binding (paired-label isotope study). Functional improvement in the glomerular damage was evidenced by a reduction of abnormal proteinuria (P < 0.05). These results suggest that MIP-2 is a major neutrophil chemoattractant contributing to influx of neutrophils in Ab-induced glomerular inflammation in the rat.

The Raji cell radioimmune assay for detecting immune complexes in human sera.

A sensitivie and simple procedure for the detection and quantitation of soluble complement (C)- fixing immune complexes in sera of patients with various disease states has been developed by utilizing C receptors on Raji cells. These cells lack membrane-bound immunoglobulin but have receptors for IgG Fc, C3b, C3d, and possibly with other C proteins. Uptake experiments showed that both aggregated human gamma globulin (AHG) and 7S IgG bound to receptors for IgG Fc; however, AHG reacted with C bound to cells only via receptors for C and this binding was much more efficient than via IgG Fc receptors. AHG was used as an in vitro model of human immune complexes and its uptake by Raji cells was quantitated by 125I-radiolabeled antihuman IgG. The limit of sensitivity of this test was 6 mug AHG/ml serum. The ability of Raji cells to detect AHG in serum depended on the amount of radioactive antibody used and the size of aggregates. The presence of an excess of C somewhat inhibited binding of AHG containing C to Raji cells. The efficient binding of AHG by receptors for C on Raji cells was used for the detection and quantitation of immune complexes in human sera. Raji cells were incubated with sera to be tested and then reacted with excess radiolabeled antihuman IgG; the amount of radioactivity bound to the washed cells was determined and referred to a standard curve of radioactive antibody uptake by cells previously incubated with increasing amounts of AHG in serum. Thereby immune complexes were detected and quantitated in serum hepatitis, systemic lupus erythematosus, vasculitis, subacute sclerosing panencephalitis, dengue hemorrhagic fever, and malignancies.

Pathophysiology of experimental glomerulonephritis in rats.

Micropuncture, clearance, immunofluorescence and light microscopy techniques were used to study kidney structure and single nephron function in rats with autologous immune complex nephritis (AICN), a membranous glomerulonephritis developing over 5 to 20 mo, in the more acute and proliferative glomerular basement membrane (GBM) nephritis and in controls. Both models are known to have clinical counterparts in human disease. Kidney functional abnormalities correlated with the degree of architectural derangement. In both AICN and anti-GBM nephritis filtration fraction fell in direct proportion to the fall in glomerular filtration rate (GFR), renal plasma flow being unchanged. Fractional electrolyte excretion increased as the GFR fell. Despite marked heterogeneity of single nephron filtration rate (SNGFR) (AICN, 5-93 nl/min; anti-GBM, 0-50 nl/min) and of proximal tubular hydrostatic pressure (4-48 mm Hg), each nephron showed almost complete glomerulotubular balance, absolute reabsorption to the late proximal convolution varying directly with filtration rate. In addition SNGFR could be related both to proximal intratubular hydrostatic pressure and to calculated glomerular capillary pressure (Pg), being lowest in those nephrons with the highest intratubular pressure. Nephrons with very high filtration rates did not apparently reach filtration equilibrium. Mean SNGFR was significantly lower in the anti-GBM group, while calculated Pg was the same in both. This probably reflects the acute and diffuse involvement of the anti-GBM lesion with different filtration characteristics from the more chronic AICN disease. Tubular damage was more marked in AICN, and extraction of p-aminohippurate was reduced in this group.

Role for endogenous and acquired peroxidase in the toxoplasmacidal activity of murine and human mononuclear phagocytes.

Oxygen products generated by the respiratory burst of mononuclear phagocytes are microbicidal to intracellular pathogens including Toxoplasma gondii. The toxicity of one of these products, H(2)O(2), is markedly amplified by the granule peroxidase of circulating phagocytes in the presence of a halide. Eosinophil peroxidase (EPO) binds firmly to the surface of T. gondii and such organisms remain viable as determined by vital staining, uptake of 2-deoxyglucose, and survival and replication in human fibroblasts. They are, however, rapidly killed by the addition of H(2)O(2) and iodide under conditions in which control organisms are unaffected. We have used EPO bound to T. gondii to explore the role of peroxidase in the toxoplasmacidal activity of mononuclear phagocytes. Resident mouse peritoneal macrophages lack a granule peroxidase and have a weak respiratory burst; toxoplasma survive and replicate within these cells. However, these cells acquire significant toxoplasmacidal activity, as assessed microscopically and by the inhibition of uracil uptake, when organisms are coated with EPO before ingestion, an effect which is decreased by the hemeprotein inhibitors, aminotriazole and azide. EPO on the surface of Toxoplasma does not increase their ingestion by macrophages or the associated respiratory burst. Monocytes from patients with hereditary myeloperoxidase deficiency have a significant toxoplasmacidal defect that is abolished when EPO-coated organisms are used. In contrast, the toxoplasmacidal defect of monocytes from chronic granulomatous disease patients is unaffected by surface-bound EPO. In these studies, replication of surviving intracellular organisms varied inversely with the magnitude of the respiratory burst: replication was greatest in fibroblasts, slightly less in resident macrophages, and least in monocytes; it was significantly greater in chronic granulomotous disease than in normal or myeloperoxidase-deficient monocytes. These studies support a role for oxygen products and endogenous peroxidase in the optimal killing of T. gondii by monocytes and demonstrate that peroxidase-negative phagocytes can utilize peroxidase on the surface of ingested organisms to augment microbicidal activity.