Distinct mechanism for antidepressant activity by blockade of central substance P receptors

The localization of substance P in brain regions that coordinate stress responses and receive convergent monoaminergic innervation suggested that substance P antagonists might have psychotherapeutic properties. Like clinically used antidepressant and anxiolytic drugs, substance P antagonists suppressed isolation-induced vocalizations in guinea pigs. In a placebo-controlled trial in patients with moderate to severe major depression, robust antidepressant effects of the substance P antagonist MK-869 were consistently observed. In preclinical studies, substance P antagonists did not interact with monoamine systems in the manner seen with established antidepressant drugs. These findings suggest that substance P may play an important role in psychiatric disorders.

Risperidone in the treatment of negative symptoms of schizophrenia: a meta-analysis

Risperidone has antiserotonergic and antidopaminergic properties that may make it more effective than conventional antipsychotic agents in the treatment of the negative symptoms of schizophrenia. Clinical trials in chronic schizophrenic patients have shown trends in favor of risperidone in the control of negative symptoms compared with haloperidol, perphenazine or zuclopenthixol, but the differences were not consistently statistically significant. A meta-analysis of the pooled results from six double-blind trials showed that risperidone at doses ranging from 4 to 8 mg/day had a significantly (p < 0.004) higher negative symptom response rate, defined as the percentage of patients with a 20% or more reduction in scores on the negative subscale of the Positive and Negative Syndrome Scale, than patients receiving active controls. The combined patient population treated with 4-8 mg/day of risperidone was 1.43 times more likely to have had a clinical response on the negative symptom subscale than the combined population treated with haloperidol, perphenazine or zuclopenthixol.

Wheat gluten challenge in schizophrenic patients

Eight chronic schizophrenic patients were maintained on a diet free of gluten, cereal grains, and milk (CM-F diet) and challenged in a double-blind manner with dietary wheat gluten and placebo. While on the CM-F diet, each patient received a daily challenge of 30 g of gluten for 5 weeks and a placebo challenge for 8 weeks. No deterioration in clinical status as measured by the BPRS was noted on gluten challenge. Serum alpha 1 acid glycoprotein measurement demonstrated no evidence of inflammatory response to gluten challenge. The data suggest that sensitivity to dietary gluten is not characteristic of young chronic schizophrenic patients.

Anatomically Based Modelling of the Human Skull and Jaw

We present here an anatomically based model of the human masticatory system that provides a framework for simulating the complex chewing process. The initial motivation for creating this model was the desire to have a computational model of the human jaw that can be used to simulate the action of simple bites, and to calculate the stresses and forces on the teeth that are involved. The model created also provides a platform that can be used to investigate other features of the masticatory system. To construct this global model, individual models of the bones of the skull and jaw were created from generic data sets. Geometric models of the muscles of mastication were also created and attached to the appropriate bones. To complete this initial model, representations of the crowns of the teeth were created and a basic model of the temporomandibular joint (TMJ) was included. The finite element method was used to solve for the stresses and strains created by the loading conditions during a clenching simulation involving the mandible bone. The model presented here is also discussed in relation to a model of the entire musculo-skeletal system being developed as part of the Physiome Project.

Occurrence of infectious upper respiratory tract disease and response to vaccination in horses on six sentinel premises in northern Colorado

REASONS FOR PERFORMING STUDY

Horses vaccinated against common agents of infectious upper respiratory disease (IURD) may not have detectable serum antibody and may not be protected from clinical disease.

OBJECTIVES

The objectives of this study were to 1) investigate the serological response of horses to vaccination against influenza virus (H3N8 and H7N7) and equine herpesviruses (EHV) in a field setting and 2) evaluate associations among vaccination status, serum antibody concentrations, and occurrences of IURD in monitored horses.

METHODS

In this study, horses on 6 Colorado premises were vaccinated parenterally against influenza virus and EHV, and serological response evaluated. Horses were monitored, and biological samples collected from individuals with clinical IURD and control horses.

RESULTS

Of 173 horses, 61 (35.3%), 21 (12.1%) and 4 (2.3%) seroconverted in response to vaccination against EHV, influenza virus H7N7 and influenza virus H3N8, respectively.

CONCLUSIONS

Outbreaks of IURD in study horses were associated with influenza virus H3N8 and Streptococcus equi infection, and serological response to vaccination with conventional products was poor.

POTENTIAL RELEVANCE

These results confirm that horses may not respond with detectable serological responses to conventional vaccination against common respiratory viruses and, therefore, suggest that alternate methods of protecting horses against common respiratory viruses should be sought.

Detection and identification of Mycoplasma from bovine mastitis infections using a nested polymerase chain reaction

A polymerase chain reaction (PCR) test was compared with culture for the detection and diagnosis of bovine Mycoplasma intramammary infection. The PCR test was applied to 24-hour Mycoplasma enrichment cultures of milk from cows with suspected mastitis and from bulk tank milk. In comparison to culture, the sensitivity and specificity of the PCR method were 96.2% and 99.1% for individual cow milk and 100% and 99.8% for the bulk tank milk, respectively. However, in discrepant cases where PCR was positive and culture was negative, the PCR test was correct; subsequent PCR tests and culturing of the individual cow's milk yielded positive results. The PCR test simultaneously detected and differentiated among 11 bovine Mycoplasma species.

Detection of cytopathic and noncytopathic bovine viral diarrhea virus in cell culture with an immunoperoxidase test

Bovine viral diarrhea virus (BVDV) antigen was detected in cell culture with an indirect immunoperoxidase (IP) procedure using a specific monoclonal antibody, and an avidin-biotin-peroxidase complex. Cytopathic and noncytopathic strains of the virus showed similar patterns of IP staining until 3 days post-infection. At six days post-infection, intensity of staining decreased in cell cultures infected with noncytopathic virus, but not with cytopathic virus. The IP procedure detected BVDV antigen in cells used to isolate virus from tissues of aborted bovine fetuses and peripheral blood lymphocytes of adult cattle. Immunoperoxidase detected BVDV isolates from 10 of 44 cases of abortion of which seven of these were noncytopathic. Noncytopathic BVDV isolates from the peripheral blood lymphocytes of 7 of 65 animals were identified.

Use of an immunoperoxidase test for the detection of bovine herpesvirus-1 in aborted fetal tissue

An indirect immunoperoxidase (IP) procedure using a specific monoclonal antibody and an avidin-biotin-peroxidase complex was developed and applied to detect virus antigen in formalin-fixed, paraffin-embedded tissue sections. This IP procedure was compared with currently used diagnostic tests for detection of virus-induced abortions caused by bovine herpesvirus-1 (BHV-1). The IP procedure was applied to detect BHV-1 antigen in sections of liver and lung from 87 aborted fetuses. Sixteen of these cases were positive for viral antigen by IP staining. Sections from both liver and lung were positive in 15 of the 16 cases. A fluorescent antibody test (FA), which was applied to acetone-fixed frozen sections of liver and lung, gave positive results on 12 of the 87 fetuses, 11 of which were also positive by IP. Seven of the 12 FA-positive cases were positive on both sections of liver and lung. When FA and IP were compared. FA had a sensitivity of 67% and IP had a sensitivity of 94%. Virus was isolated from one of the 67 cases tested. The tissues in which antigen was most frequently detected by IP were liver, lung, and kidney. Distinct multifocal staining was seen in positive sections of all these tissues.

Enzyme-linked immunosorbent assay for detection of feline herpesvirus 1 IgG in serum, aqueous humor, and cerebrospinal fluid

Feline herpesvirus 1 (FHV) is an important cause of feline ocular and respiratory disease, but the role the virus plays in central nervous system disease of cats has not been explored. The study described here was performed to validate an indirect enzyme-linked immunosorbent assay (ELISA) to detect FHV-specific IgG antibodies for use in feline epidemiologic, ocular, and central nervous system disease studies. The indirect IgG ELISA was applied to serum, aqueous humor, and cerebrospinal fluid from cats. Serum FHV IgG ELISA results were compared with those of serum neutralization in client-owned cats and laboratory-housed cats following vaccination. Of the 100 client-owned cats tested by ELISA, 97 had detectable FHV IgG; 95 had titers >32. The FHV IgG ELISA was more sensitive than serum neutralization and could be used with aqueous humor and cerebrospinal fluid. Cats with inflammatory central nervous system or ocular diseases had significant leakage of serum proteins into aqueous humor and cerebrospinal fluid, necessitating use of cutoff values derived from serum when these fluids were assessed.

Use of an immunoperoxidase technique to detect equine herpesvirus-1 antigen in formalin-fixed paraffin-embedded equine fetal tissues

An indirect immunoperoxidase (IP) procedure using the avidin-biotin-peroxidase complex detection technique was developed to detect viral equine herpesvirus-1 (EHV-1) antigen in formalin-fixed paraffin-embedded tissues from aborted equine fetuses. The procedure was applied to liver, lung, and other tissues from 20 cases of confirmed or suspected EHV-1-induced abortions. Specific staining was observed in tissue sections from EHV-1-infected fetuses. Positive IP staining was present in tissues of 7 cases that were also positive by fluorescent antibody (FA) and virus isolation (VI) and that had typical histologic lesions. There was no IP staining in 7 cases that had no histologic lesions and negative FA and VI results. Five cases had typical histologic lesions and positive results in only 1 laboratory test; 3 were positive by VI and 2 by FA. Liver of 1 case was positive by IP, but tissues were too autolytic for other tests to be evaluated.

Detection of cold-adapted vaccine-strain influenza virus using two commercial assays

Because of the contagious nature of influenza virus it is necessary to identify infected individuals after the virus is introduced into a population. The aim of this study was to characterise influenza virus detection with commercially available assays after intranasal vaccinating horses with cold-adapted influenza virus. Seven horses were vaccinated and placed with 3 unvaccinated horses. Nasal secretion samples were evaluated using 2 antigen detection assays. All 10 horses were positive in the Flu OIA assay during the study period, but only one horse was positive on one sample using the Directigen Flu A assay. Horses were most likely to be positive during the first 3 days following vaccination, and several horses were intermittently positive for several days after this. Obtaining positive test results from nonvaccinated, incontact horses suggests they became infected with vaccine-strain virus that was shed by vaccinated horses. These results are important for the correct interpretation of influenza antigen detection tests in situations when this modified-live intranasal vaccine has been used.

Evaluation of an antigen-capture ELISA for the detection of bovine herpesvirus type 1 shedding from feedlot cattle

A total of 457 nasal swab specimens from cases of respiratory disease in 2 feed lots were evaluated for the detection of bovine herpesvirus Type 1 (BHV-1) by ELISA. Thirty-three were found to be positive for BHV-1 by the recovery of infectious virus and 21 of these were positive by ELISA, yielding a sensitivity of 64%. Fifteen other virus isolations were made and included bovine viral diarrhea viruses, rhinoviruses and parainfluenza Type 3 viruses; none of these cases were positive with the BHV-1 ELISA. Specificity of the ELISA was 100%. Eighty percent of the specimens with BHV-1 titers greater than 10(5) TCID50 were detected by ELISA; the median amount of virus in positive specimens that were detected by ELISA was 7 X 10(5) TCID50 and the median amount of virus in specimens not detected was 1.5 X 10(4) TCID50. BHV-1 infection was most frequently diagnosed in feedlot cattle that had been in the feedlot for 40-80 days. Approximately half of the infected cattle were carrying virus-neutralizing antibodies in their serum.

Detection of cattle infected with bovine viral diarrhea virus using nucleic acid hybridization

A ribonucleic acid (RNA) hybridization assay to identify cattle infected by bovine viral diarrhea virus (BVDV) is described. The RNA probe was derived from the coding region at the 3' end of the genome of the NADL strain of BVDV. Total RNA from infected cell cultures or peripheral blood leukocytes from suspect animals was extracted and applied to nylon membranes with a slot blot apparatus. Peripheral blood leukocytes were tested concurrently for BVDV by virus isolation. The results of hybridization and virus isolation were in agreement for 92% of the cases. When compared with virus isolation, hybridization had a sensitivity of detection of 59.5% and a specificity of 95%. Cross-reactivity to RNA extracts of border disease virus-infected cells was noted. No cross-reactivity was detected to other common bovine viruses (bovine herpesvirus-1, bovine respiratory syncytial virus, parainfluenza-3 virus, and bluetongue virus), to viruses classified in related families (equine arteritis virus and Venezuelan equine encephalitis virus), or to viruses having similar genomic organization (dengue virus type 2 and Japanese encephalitis virus).

Use of isolated immature-stage B cells to understand negative selection and tolerance induction at the molecular level

Encounter with antigen by newly developing antigen receptor-positive B cells leads to negative selection. This process positions the B cell antigen receptor (BCR) in a central role for initiating the process of negative selection and suggests developmental regulation of its signaling. The observation that immature B cells are more susceptible to negative selection than are mature B cells has been demonstrated in a number of in vitro and in vivo model systems and support the idea of developmental regulation of BCR-initiated responses. Since identical antigen receptors are expressed on immature and mature B cells, the critical fate-determining distinction between these developmental stages must lie downstream of the receptor-ligand interaction itself, in the form of different BCR-linked signaling processes or with different secondary events occurring subsequent to BCR cross-linking. To address the first possibility, our laboratory and others have sought to define the differences in BCR-mediated signal transduction in immature and mature B lymphocytes. In this review article we will discuss current in vitro systems to study this question in primary, nontransformed murine B lymphocytes. In addition, we will discuss our previously published work in order to illustrate how these model systems have been useful in beginning to unravel the molecular basis for immune B cell negative selection and tolerance.

Epitope specificity of the bovine antibody response to the gIII glycoprotein of bovine herpesvirus type 1

A panel of monoclonal antibodies (MAbs) to BHV-1, specific for gI and gIII glycoproteins and for a nonglycosylated core protein p100, was used to examine the epitope specificity of the immune response to the virus in naturally exposed and experimentally infected cattle. Sera from experimentally infected calves were analyzed in a competition ELISA (C-ELISA). Antibody to an epitope on gIII appeared as early as 4 days post infection, although virus-neutralizing antibody did not appear until day 8 or later. Antibody production peaked at 13 to 18 days post infection but the level of antibody to each gIII epitope varied. Competition by sera from cattle naturally exposed to BHV-1 was analyzed as a function of the virus neutralization (VN) titer of these sera. Competition with most of the MAbs correlated linearly with neutralization titer. However, competition with 2 of the MAbs, one specific for gIII and one specific for gI, was maximal even at the lowest neutralization titer, and competition with another MAb, specific for a non-glycosylated core protein, p100, was negative. Selected sera from the naturally exposed group were also examined by radioimmunprecipitation, and were shown to react predominantly with gI, gIII and gIV glycoproteins and in a few shown to react predominantly with gI, gIII and gIV glycoproteins and in a few MAbs were determined, and it was found that neutralization was enhanced by certain combinations. A mutually exclusive relationship between neutralization enhancement and competition for binding by MAbs (as determined by reciprocal C-ELISA) indicated an epitope-specific, rather than antibody-specific, mechanism for neutralization enhancement.

Intussusception in a premature infant simulating necrotising enterocolitis

Intussusception in older infants is manifested by bloody stools, colicky abdominal pain and a palpable abdominal mass. In neonates the symptoms are often restricted to vomiting, guaiac positive stools and abdominal distension. These symptoms closely mimic necrotising enterocolitis. Surgical treatment of necrotising enterocolitis should be postponed until perforation of the gastrointestinal tract has occurred, whereas, prompt surgical treatment is recommended for intussusception. We report a case of intussusception that simulated necrotising enterocolitis in a 740 grammes premature infant in the second week of life. The clinical and radiographic features are described and the difficulty in distinction between the two conditions is emphasised. Neonatologists and paediatric surgeons should always include intussusception in the differential diagnosis of abdominal distension and guaiac positive stools in small premature infants.

Concurrent outbreaks of Salmonella Typhimurium in South Australia

The Communicable Disease Control Branch of the South Australian Health Commission received 45 laboratory notifications of Salmonella between 23 December 1996 and 17 January 1997. A rapid screening test, undertaken by the Institute of Medical and Veterinary Sciences, Adelaide, was the first indication that this was more than one outbreak, prompting the establishment of separate investigations. Three Salmonella Typhimurium (S. Typhimurium) phage types were subsequently identified. Investigations are continuing into an outbreak of S. Typhimurium phage type (PT) 64, while investigations failed to identify any association between four cases of PT 44. As of 12 February 1997, 71 notifications had been confirmed as S. Typhimurium PT 135. Epidemiological investigations found this outbreak was associated with consumption of bread rolls with a meat filling distributed through local Asian grocery stores from a home-based manufacturer. The product was voluntarily withdrawn and there have been no new cases of PT 135.

Neonatal suppression with anti-Ia antibody. III. In vivo responses to the type 2 antigen TNP-Ficoll

We studied the response to thymus-independent type 2 (type 2) Ag in mice suppressed from birth with anti-Ia antibody. Although these mice have significantly reduced numbers of surface IgM+ cells and reduced or absent levels of Ia-restricted Th cell activity, their IgM antibody response to the type 2 Ag TNP-Ficoll was unaffected whereas that to the prototypic thymus-dependent Ag SRBC was predictably eliminated. These data suggest that an in vivo antibody response can be made to type 2 Ag in the absence of Ia-dependent cellular interactions. The surface IgM+IgD-Ia- B cells that are found in the anti-Ia antibody-suppressed mouse may represent an expanded population of Ia-independent, type 2 Ag-sensitive B cells normally present as a smaller proportion of the splenic lymphocyte population. Thymus-dependent responses, which have been shown to have an absolute requirement for an Ia-dependent interaction, are absent in these animals.

Evaluation of serologic and viral detection methods for diagnosing feline herpesvirus-1 infection in cats with acute respiratory tract or chronic ocular disease

OBJECTIVE

To determine the value of virus isolation (VI), immunofluorescent antibody (IFA) assay, serum neutralization (SN), and ELISA for the diagnosis of clinical feline herpesvirus-1 (FHV-1) infection in cats.

ANIMALS

46 clinically normal cats, 17 cats with signs of acute respiratory tract disease, and 38 cats with signs of chronic ocular disease.

PROCEDURE

Conjunctival swabs for VI, conjunctival scrapings for IFA testing, and venous blood samples for SN or ELISA testing were obtained from all cats.

RESULTS

FHV-1 was detected in 10.9 and 28.3% of clinically normal cats and in 18.2 and 33.3% of cats with FHV-1-associated disease by VI and the IFA assay, respectively. There were no significant differences in the viral detection rate between cats with acute respiratory tract disease and cats with chronic ocular disease or between diseased cats and clinically normal cats; however, FHV-1 was never detected by both methods in clinically normal cats. Overall FHV-1 seroprevalence was 97% when tested by ELISA and 66% when tested by SN. Seroprevalence did not vary significantly among the 3 groups for either serologic test. Magnitude of SN and ELISA titers varied greatly but independently of presence or absence of clinical signs of FHV-1-associated disease. Sensitivity, specificity, and positive and negative predictive values were assessed for VI and the IFA assay--jointly and individually--and for each SN and ELISA titer magnitude. Values never all exceeded 50%.

CLINICAL IMPLICATIONS

Because FHV-1 can be detected commonly in clinically normal cats by the IFA assay or VI, neither test appears to aid in the clinical diagnosis of FHV-1 infection. Seroprevalence does not appear to vary between affected and clinically normal cats. SN, ELISA, VI, and the IFA assay appear to be of limited value in the diagnosis of FHV-1-associated disease in cats. Concurrent assessment of the IFA assay and VI results may permit exclusion of FHV-1 as an etiologic agent if results of both tests are negative.

Serologic prevalence of selected infectious diseases in cats with uveitis

Serologic evidence of infection by Toxoplasma gondii, feline leukemia virus, feline coronaviruses, or feline immunodeficiency virus (FIV) is commonly found in cats with uveitis. Serum samples from 124 cats with uveitis were assayed by use of ELISA for the detection of T gondii-specific immunoglobulin M (IgM), IgG, and circulating antigens (Ag), as well as an ELISA for feline leukemia virus Ag, an ELISA for antibodies to FIV, and an indirect fluorescent antibody assay for antibodies to feline coronaviruses. Serologic evidence of infection by 1 or more of the infectious agents was detected in 83.1% of the samples. Serologic evidence of T gondii infection, defined as the detection of T gondii-specific IgM, IgG, or Ag in serum, was found in 74.2% of the samples. The seroprevalence of T gondii infection was significantly greater in cats with uveitis than in healthy cats from a similar geographic area. Serum samples from cats with serologic evidence of both T gondii and FIV infections were more likely to contain T gondii-specific IgM without IgG than samples from cats with serologic evidence of T gondii infection alone. Cats with serologic evidence of FIV and T gondii coinfection had a higher T gondii-specific IgM titer geometric mean and a lower T gondii-specific IgG titer geometric mean than did cats with serologic evidence of T gondii infection alone. Serologic evaluation for T gondii infection should include assays that detect IgM, IgG, and Ag, particularly in cats coinfected with FIV.

Interferon-gamma suppresses B cell stimulation factor (BSF-1) induction of class II MHC determinants on B cells

The data presented in this manuscript extend our previous observations that recombinant interferon-gamma (reIFN-gamma) can suppress anti-immunoglobulin (anti-Ig)-stimulated B cell proliferation, and demonstrate that reIFN-gamma can also suppress B cell stimulation factor type 1 (BSF-1)-stimulated increases in expression of MHC class II molecules (Ia) on B cells. This suppression is most effective when relatively low concentrations of BSF-1 are employed, but is still very substantial even when optimal concentrations of BSF-1 were used. This suppression is also observed when size-separated small B cells which are devoid of detectable macrophages or NK cells are cultured with BSF-1 and reIFN-gamma, thus suggesting that IFN-gamma-mediated inhibition is a consequence of a direct effect on the B cells. Incubation of B cells with reIFN-gamma for 24 hr before their culture with BSF-1 did not prevent BSF-1-stimulated increases in sIa. This finding supports the contention that the effect of IFN-gamma is not mediated via the stimulation of "suppressor" influences in these cell cultures. The inhibition of B cell activation by IFN-gamma occurs within the first 3 hr after the onset of culture, as demonstrated by the inability of antibody to IFN-gamma to totally reverse the IFN-gamma-mediated suppressive effects on B cell proliferation if it is added later than 3 hr after the onset of culture. These results suggest a role for IFN-gamma in down-regulating the ability of B cells to function as antigen-presenting cells in non-cognate T cell-dependent responses.

Neonatal suppression with anti-Ia antibody. III. In vivo responses to the type 2 antigen TNP-Ficoll

We studied the response to thymus-independent type 2 (type 2) Ag in mice suppressed from birth with anti-Ia antibody. Although these mice have significantly reduced numbers of surface IgM+ cells and reduced or absent levels of Ia-restricted Th cell activity, their IgM antibody response to the type 2 Ag TNP-Ficoll was unaffected whereas that to the prototypic thymus-dependent Ag SRBC was predictably eliminated. These data suggest that an in vivo antibody response can be made to type 2 Ag in the absence of Ia-dependent cellular interactions. The surface IgM+IgD-Ia- B cells that are found in the anti-Ia antibody-suppressed mouse may represent an expanded population of Ia-independent, type 2 Ag-sensitive B cells normally present as a smaller proportion of the splenic lymphocyte population. Thymus-dependent responses, which have been shown to have an absolute requirement for an Ia-dependent interaction, are absent in these animals.

Monitoring and detection of acute viral respiratory tract disease in horses

OBJECTIVE

To develop a system to monitor and detect acute infections of the upper respiratory tract (i.e., nares, nasopharynx, and pharynx) in horses and to assess the association among specific viral infections, risk factors, and clinical signs of disease.

DESIGN

Prospective study.

ANIMALS

151 horses with clinical signs of acute infectious upper respiratory tract disease (IURD) from 56 premises in Colorado.

PROCEDURE

Health management data, blood samples, and nasal or nasopharyngeal swab samples were obtained for 151 horses with clinical signs of acute IURD. Of these horses, 112 had an additional blood sample obtained during convalescence and were considered to have complete sample sets. Samples were tested for evidence of respiratory tract infection by use of ELISA, virus isolation, and serologic testing of paired serum samples.

RESULTS

Viral infections were identified in 65 horses with complete sample sets; influenza virus infection was identified in 43 horses, equine herpesvirus (EHV) infection in 18, and mixed influenza virus and EHV infections in 4. On 14 premises, samples were obtained from more than 1 affected horse. Viral infections were identified in horses on 11 of 14 premises. Equine herpesviruses were isolated from 10 horses. A relationship was not found between vaccination history and identification of EHV or influenza virus infections. An infection with EHV was less likely to be identified in horses with initial (acute) antibody titers > 1:16 to EHV.

CLINICAL IMPLICATIONS

Influenza virus (specifically, A/equine/2) was the most common virus associated with acute IURD. Use of multiple diagnostic tests and obtaining samples from more than 1 horse in an outbreak may improve detection of viral infections.

Interferon-gamma suppresses B cell stimulation factor (BSF-1) induction of class II MHC determinants on B cells

The data presented in this manuscript extend our previous observations that recombinant interferon-gamma (reIFN-gamma) can suppress anti-immunoglobulin (anti-Ig)-stimulated B cell proliferation, and demonstrate that reIFN-gamma can also suppress B cell stimulation factor type 1 (BSF-1)-stimulated increases in expression of MHC class II molecules (Ia) on B cells. This suppression is most effective when relatively low concentrations of BSF-1 are employed, but is still very substantial even when optimal concentrations of BSF-1 were used. This suppression is also observed when size-separated small B cells which are devoid of detectable macrophages or NK cells are cultured with BSF-1 and reIFN-gamma, thus suggesting that IFN-gamma-mediated inhibition is a consequence of a direct effect on the B cells. Incubation of B cells with reIFN-gamma for 24 hr before their culture with BSF-1 did not prevent BSF-1-stimulated increases in sIa. This finding supports the contention that the effect of IFN-gamma is not mediated via the stimulation of "suppressor" influences in these cell cultures. The inhibition of B cell activation by IFN-gamma occurs within the first 3 hr after the onset of culture, as demonstrated by the inability of antibody to IFN-gamma to totally reverse the IFN-gamma-mediated suppressive effects on B cell proliferation if it is added later than 3 hr after the onset of culture. These results suggest a role for IFN-gamma in down-regulating the ability of B cells to function as antigen-presenting cells in non-cognate T cell-dependent responses.