Isolation of Corynebacterium kutscheri from aged Syrian hamsters (Mesocricetus auratus).

Corynebacterium kutscheri was isolated from the oral cavities of 12 male Syrian hamsters (Mesocricetus auratus) which were about 12 months old. At 1, 5, and 9 months after initial isolation of C. kutscheri from the oral cavity, hamsters were euthanatized, and attempts were made to culture C. kutscheri from 13 additional sites. Corynebacterium kutscheri was isolated from nine hamsters, and regardless of the hamsters' ages, the organisms were most frequently isolated from the oral cavity (100%), esophagus (100%), cecal content (100%), and colon and rectum (88.9%). Isolation rates in the nasal cavity were 66.7%, followed by 55.5% in the trachea and 33.3% in the submaxillary lymph nodes. The number of the organisms found in the submaxillary lymph nodes and esophagus was 10(3) to 10(4) CFU/g. The number found in the cecal content and in the colon and rectum was 10(2) to 10(5) CFU/g. The organisms were not isolated from lung, stomach, kidney, spleen, and mesenteric lymph node tissues. The hamsters had neither clinical signs nor lesions. However, 7 of 12 animals had low agglutinating antibody titers. The Syrian hamster can therefore be an asymptomatic carrier of C. kutscheri.     

Comparison of methods to diagnose an epizootic of Corynebacterium kutscheri pneumonia in rats

An outbreak of Corynebacterium kutscheri pneumonia occurred in a colony of laboratory rats. Diagnostic methods compared on a prospective basis included (1) an enzyme-linked immunosorbent assay (ELISA) for serum antibody to C. kutscheri; (2) C. kutscheri isolation from retrograde nasal wash, cervical lymph nodes, tracheal wash, lung homogenate; and (3) histopathology. C. kutscheri was isolated from one or more of the cultured sites from suspected cases, but no individual rat yielded C. kutscheri from all of the sites. The presence of histological lung lesions was the most frequent indicator of infection (8 of 9 suspected cases), followed by isolation of C. kutscheri from lung homogenate (5 of 6), ELISA for serum antibody (6 of 8), and isolation of C. kutscheri from cervical lymph node (4 of 8). Isolation of C. kutscheri from nasal wash (1 of 9) was the least sensitive indicator of infection. ELISA antibody was not detected in rats which had normal lungs and did not harbor C. kutscheri. It was concluded that ELISA provides noninvasive means for detecting infection and cervical lymph node culture increase the potential for successful isolation of the agent in C. kutscheri infected rats.     

The effect of selected viruses on Corynebacterium kutscheri infection in rats

The influence of selected viral pathogens on rats that were previously infected with Corynebacterium kutscheri was investigated. A series of three separate experiments were performed to test the effect of sialodacryoadenitis virus, Sendai virus and rat virus. In each experiment, weanling rats were divided into three groups (C. kutscheri-inoculated, virus-inoculated and C. kutscheri plus virus-inoculated). Two groups were inoculated oronasally with C. kutscheri to establish subclinical infections. Two weeks later, two groups were inoculated intranasally with virus. At 5 weeks, the prevalence of C. kutscheri recovery from oral cavity and submaxillary lymph node and the prevalence of overt pseudotuberculosis was compared between treatment groups. Seroconversion of rats to C. kutscheri was measured by microagglutination and viruses by indirect immunofluorescence assays. Infection of rats with sialodacryoadenitis virus, Sendai virus or rat virus had no discernable effect on C. kutscheri-infected rats.     

Selective medium for Corynebacterium kutscheri and localization of the organism in mice and rats

A new selective medium for isolation of Corynebacterium kutscheri (CK) from animals suffering subclinical infection was made by adding furazolidone, nalidixic acid and corimycin to the heart infusion agar base, this being named FNC agar. The FNC agar inhibited the growth of gram-negative rods, Pseudomonas aeruginosa, Proteus sp. and gram-positive cocci but did not affect the growth of CK. When this medium was used to isolate CK from the oral cavity and cecal contents of mice and rats, two of 6 conventional mouse colonies and three of 8 conventional rat colonies were found to be infected, with isolation of the organism from 19 mice and 12 rats in total. The animals showed neither clinical signs nor lesions, but the antibody was positive in 11 mice and 10 rats. In mice and rats inoculated orally with 4 x 10(8) and 1 x 10(9) organisms, respectively, CK was isolated for 20 weeks post-inoculation by use FNC agar. The isolation rate of the organism was the highest in the oral cavities of both inoculated mice and rats, and also in the submaxillary lymph nodes of the inoculated rats. The organism was also recovered from the cecal contents of more than half of the inoculated mice and rats. Thus, it was considered that FNC agar was useful in isolating CK from the oral cavity and cecal contents of mice and rats with subclinical infection of the organism.     

Detection of Corynebacterium kutscheri in the faeces of subclinically infected mice

Mice were infected experimentally and subclinically with Corynebacterium kutscheri to recover the organism from mice faeces. The faeces were then cultured using selective furazolidone-nalidixic acid-colimycin agar. The number of C. kutscheri per gram of fresh faeces varied from mouse to mouse, but once established in the intestine, the organism was excreted in the faeces for at least five months. Viable bacteria were detected in most of the faecal samples, including those stored in the animal room for five days. The number of organisms in the stored faeces decreased gradually but did not differ significantly from those in the fresh faeces until they had been stored for more than three days. Many infected mice excreted between 10(4.77) and 10(5.37) colony forming units (CFU) of C. kutscheri per day in their faeces, and one mouse even excreted 10(3.74) CFU at eight weeks postinfection. These values showed little daily variation. Our present study showed that subclinically infected mice discharged the organism continuously and persistently in their faeces. Therefore, faecal samples would be useful for monitoring infection with C. kutscheri in living mice in a manner that is not stressful for the animals.     

Naturally occurring subclinical Corynebacterium kutscheri infection in laboratory rats: strain and age related antibody response

Naturally occurring subclinical Corynebacterium kutscheri infection was analyzed by antibody response related to the strain of rats. Wistar-Lewis, Wistar and Spraque-Dawley rats were high responders in seroconversion rates and antibody titers, while Brown Norway and Fischer rats were low responders. The antibody response was related to age also. Some young rats had maternal antibody to C. kutscheri, but antibody disappeared before 8 weeks of age. Rats were antibody-negative for several months thereafter and became antibody-positive after 6 months of age. The antibody response was highest at 8 to 9 months of age in subclinical C. kutscheri infection. This antibody response was very late, compared to the antibody response to Sendai virus and Mycoplasma infections.     

Corynebacterium Pseudotuberculosis Infection in Goats VII.

Six castrated male kids from 2 herds free from caseous lymphadenitis, were inoculated subcutaneously with about 1 million colony forming units of a Corynebacterium pseudotuberculosis strain isolated from goat. The animals exhibited a febrile response and marked inflammatory reaction at the inoculation site during the first days after infection. Post mortem examination carried out 2 months after inoculation revealed abscesses in the regional lymph node (Inn. subiliaci) of all animals, in 3 of which lesions also appeared in other lymph nodes. The antibody titre (mean value) in the bacterial agglutination test peaked during the first 2 weeks following inoculation, while the titre in the hemolysis inhibition test began to rise from 2–3 weeks after the infection and continued to increase during the rest of the investigation period (9 weeks after inoculation). Hemoglobin and hematocrit levels decreased significantly after inoculation, and remained below the preinfection levels for 2 weeks. A significant leucocytosis was also seen during the same period. The present investigation indicates that subcutaneous inoculation with C. pseudotuberculosis might be a suitable challenge system to study the efficacy of vaccines against caseous lymphadenitis in goats.     

Serological surveys of Corynebacterium kutscheri infection in mice and rats

Serological surveys of mice and rats naturally infected with Corynebacterium kutscheri were performed by examining serum samples collected from breeder and laboratory colonies between 1981 and 1983. Among 756 mice from 73 conventional colonies, only 4 animals (0.5%) from 3 colonies (4.1%) developed C. kutscheri antibody of 1:40 to 1:2, 560 titers. Three of them suffered from abscess caused by the organism. Regarding a titer of 1:40 or higher as reliably positive, 87 (13.0%) of 669 conventional rats or 20 (32.8%) of 61 colonies were found to be infected with the organism. The antibodies were detected in both types of animals older than 6 months of age. No lesions caused by C. kutscheri were found in almost all the rats examined. Germ-free and SPF mice and rats were all negative for antibody at 1:5 serum dilution.     

Methicillin-resistant Staphylococcus aureus ST398 contamination and transmission in pigs after a low dose inoculation

Aims: Methicillin‐resistant Staphylococcus aureus (MRSA) ST398 has recently been described as a zoonotic agent. Its transmission between animals seems to be a pivotal factor in its emergence and dissemination. This experimental trial was performed to describe MRSA ST398 contamination and transmission in pigs after a low dose inoculation. Methods and results: Twelve specific pathogen‐free (SPF) pigs were randomly divided between two separate pens. Three pigs in each pen received a nasal inoculation of 2 × 10⁴ colony‐forming units per animal, and three naïve pigs were left in contact with them. Every 2 days and at necropsy, different samples were screened for MRSA. It was detected in nasal swabs from five inoculated and three naïve contact pigs, as early as 1 day after inoculation. MRSA was also found in environmental wipes but never in faecal samples. At necropsy, MRSA was detected in the lymph nodes of two contact pigs and in the tonsils and lymph nodes of three inoculated pigs. Twelve other SPF pigs were included as negative control in a separate room. Conclusion: This experiment showed that inoculation of a low dose of MRSA ST398 could lead to the horizontal transmission of the bacterium between pigs, the contamination of mandibular lymph nodes and the contamination of the environment without faecal carriage. Significance and Impact of the Study: The minimal inoculated dose via nasal route to observe transmission of MRSA ST398 between pigs is equal or lower to 2 × 10⁴ colony‐forming units per animal, and faecal excretion seems not to be a necessary condition for horizontal transmission.     

Survival of Escherichia coli O157 in faeces of experimentally infected rats and domestic pigeons

In order to evaluate the role of some synanthropic animals in the spreading of Escherichia coli O157, laboratory rats and domestic pigeons were experimentally infected per os with E. coli O157. Rats infected with 10(5) colony forming units (cfu) (n = 5) and 10(9) cfu (n = 5) shed E. coli O157 for 2 +/- 1.7 d and 9.8 +/- 1.3 d, respectively. In the faeces of infected rats stored at 4 degrees C in a moist environment, at 4 degrees C in a dry environment or at 20 degrees C in a moist environment, E. coli O157 survived for 34 weeks. When stored at 20 degrees C or - 20 degrees C in a dry environment, E. coli O157 survived for greater than or = 36 weeks. Pigeons infected with 10(5) cfu (n = 5) and 10(9) cfu (n = 5) shed the pathogen for 14.8 +/- 3.4 d and 20.2 +/- 5.2 d, respectively. Both species, rats and pigeons, can be important in spreading of the E. coli O157 infection in cattle.     

Studies of the mechanism of bacterial resistance to complement-mediated killing. V. IgG and F(ab')2 mediate killing of E. coli 0111B4 by the alternative complement pathway without increasing C5b-9 deposition

The mechanism of antibody-dependent complement-(C) mediated killing of Escherichia coli 0111B4, strain 12015 (12015), was examined. 12015 was resistant to serum killing when incubated in hypogammaglobulinemic serum (H gamma S) or pooled normal human serum (NHS) that had been previously adsorbed to remove specific antibody (Abs NHS). Presensitization with immune rabbit serum or purified immune rabbit IgG resulted in 1 to 3 log killing when 5 X 10(8) colony forming units (CFU)/ml were incubated in 10 to 40% Abs NHS. Binding of 125I-C3 and 131I-C9 to the bacterial surface of the presensitized and the nonpresensitized strain was quantitated when these organisms were incubated in 10, 20, and 40% Abs NHS. Stable binding of up to 3.0 X 10(5) molecules of C3 and 8.0 X 10(4) molecules of C9 to presensitized and nonpresensitized isolates occurred in the highest concentration of serum, but there was no killing without presensitization. Similar results were found when Abs NHS was chelated with ethylene bis glycoltetraacetic acid containing 2 mM MgCl2 (Mg EGTA) to block classical pathway activation, indicating that antibody mediated the bactericidal reaction through the alternative pathway. Deposition of C3 and C9 and killing of 120 15 in 10% Abs NHS or 10% H gamma S was measured after presensitization with increasing amounts of IgG, F(ab')2, or Fab'. There was a dose-dependent increase in C3 deposition and killing, but only minimal change in C9 binding when 1.0 X 10(3) to 3.2 X 10(4) IgG or F(ab')2/CFU were bound to the bacterial surface. In contrast, there was no increase in C3 or C9 binding and no bacterial killing when 1 X 10(3) to 3.4 X 10(4) molecules Fab'/CFU were bound to the bacterial surface. These experiments show that immune IgG and F(ab')2 can mediate killing of E. Coli 0111B4 by the alternative pathway without changing the extent of terminal C component attachment to the bacterial surface.     

Nippostrongylus brasiliensis: radioresistant IgE antibody-forming cells in infected rats

In Nippostrongylus brasiliensis-infected rats, anti-N. brasiliensis IgE antibody production was observed at 20 weeks postinfection, long after the worms, as a source of antigen, had been expelled. The persistent IgE production was not abrogated after whole body irradiation (800 R) administered at 12 or 20 weeks, suggesting the participation of radioresistant IgE-forming cells. Help of T cells and recruitment of B memory cells in the irradiated rats seems to be ruled out by the findings that the irradiation completely inhibited the initiation of anti-N. brasiliensis IgE production in rats shortly after the infection with N. brasiliensis or after primary and secondary immunization with N. brasiliensis-antigen. Moreover, clearance of anti-N. brasiliensis IgE antibody from circulation did not seem to be crucially affected by the irradiation. The radioresistant cells forming anti-N. brasiliensis IgE were most productive in mesenteric lymph nodes as compared to other lymph nodes. The recognition of antigens fractionated by chromatography on Sephadex G-200 was the same for IgE-forming cells from rats 12 weeks after infection as for those from 3 weeks after infection. Based on these results, one of the mechanisms of persistent elevation of IgE antibody in the host infected with helminth parasites might be explained by the participation of radioresistant IgE-forming cells.     

Detection of Corynebacterium kutscheri from the oral cavity of rats.

A simple and useful method for the detection of C. kutscheri from the oral cavity of living rats was devised. In 10 sacrificed rats from two naturally and subclinically infected conventional colonies, 10(4.28) or 10(3.84) CFU/ml C. kutscheri were isolated from upper incisor swab extractions, while 10(1.38) or 10(1.58) and < 10 or 10(1.56) CFU/ml from the upper soft palate and pharynx, respectively. In another survey with 26 living animals, which were reared on the same rack, organisms were detected from the upper incisor and gingival swabs in 15 of 26 rats (57.7%). The results were reproducible at a second survey 10 days later. No organisms were isolated from any sites of the orally negative rats. These results indicated that culture of swab specimens from the upper incisors and gingivae of incisors is useful for the detection of C. kutscheri infection in living rats.     

Formulation of a Streptomyces Biocontrol Agent for the Suppression of Rhizoctonia Damping-off in Tomato Transplants

Formulations of a Streptomyces biological control agent for Rhizoctonia damping-off in tomato seedlings were developed for the first time from vegetative propagules obtained from actively growing, nonsporulating liquid cultures. Alginate beads, durum flour (starch) granules, and talcum powder formulation of this new actinomycetous antagonist (Streptomyces sp. Di-944) isolated from the rhizosphere of field-grown tomato (Lycopersicon esculentum) suppressed damping-off caused by Rhizoctonia solani in tomato plug transplants (cv. Bonny Best) in a peat-based, soilless potting mix under greenhouse conditions. For formulations, vegetative biomass of Streptomyces sp. Di-944 from 3-day-old liquid fermentation in yeast extract–malt extract–glucose broth was lyophilized and pulverized to obtain fragments of viable vegetative filaments. The pulverized biomass had an initial viable count of 2 × 10⁷colony forming units/g and retained 100% viability for 2 weeks when stored at 4°C. Formulations stored at 4°C had a longer shelf life than those stored at 24°C based on viability at 2-week intervals over a 6-month storage period. In addition, dual culture tests showed declining efficacy for surviving Streptomyces propagules in formulations during this storage period. At 4°C, the powder and granular formulations were found to be the most stable and were shown to be 100% viable after 14 and 10 weeks of storage, respectively. However, at the end of 24 weeks, the number of viable propagules in the powder and granular formulations declined to 1.2 × 10⁵ and 7 × 10³ colony forming units/g, respectively. Alginate beads were the least stable in storage. Even at 4°C, 6.9 × 10⁴ and 7.3 × 10² viable propagules/g formulation were detected at the end of 12 and 24 weeks, respectively. The talcum powder formulation delivered to tomato seeds as a seed-coating was the most effective biocontrol treatment. It suppressed damping-off in 10-day-old tomato transplants by almost 90% compared to 30 and 22% damping-off reduction when alginate beads or starch granules were delivered concomitantly with tomato seeds. Seed-coating with powder formulation of the biocontrol agent was as effective as drench application of the fungicide, oxine benzoate (No-Damp), in controlling Rhizoctonia damping-off and superior to the commercial biocontrol agent, Streptomyces griseoviridis (Mycostop), applied to tomato seeds as seed-coating.     

Field trial of a live streptomycin dependent Pasteurella multocida serotype A:12 vaccine in rabbits

A live, streptomycin dependent, Pasteurella multocida (SDPM) serotype A:12 vaccine was evaluated for preventing pasteurellosis in two commercial rabbitries. Rabbits were inoculated intranasally at 5 weeks old with either 0.25 ml of vaccine containing 10(8) colony forming units/ml or 0.25 ml of diluent (control). A proportion of rabbits received a second intranasal inoculation 1 month later. Partial protection against P. multocida infection was observed 1 and 2 months after inoculation in rabbits given only one dose of vaccine. The incidence of clinical signs of pasteurellosis was similar in vaccinated and nonvaccinated market-age rabbits inoculated 4 to 6 weeks previously. In does maintained in the breeding colony, P. multocida infection and upper respiratory disease occurred more frequently in vaccinated than nonvaccinated rabbits. Humoral antibody responses (IgA, IgM, IgG) followed longitudinally were similar in vaccinated and nonvaccinated does. Hence, the SDPM vaccine was not efficacious in controlling P. multocida infection at these two rabbitries.     

Intrapulmonary BCG cell wall vaccination in mice

Mice of two inbred strains, Balb/c and C3H/He, were given three dosages of mycobacterium bovis BCG (5 X 10(4), 5 X 10(2) and 5 colony forming units) by either the intravenous route or by a direct intratracheal (non-aerosol) route. The magnitude of the infectivity of these inoculae given by these routes was assessed by measurement of weight changes and mycobacterial multiplication in the spleen and lung. As expected, the Balb/c strain was more susceptible to infection than the C3H/He strain. However, for both strains, infection by the intratracheal route resulted in mycobacterial counts in the lungs which were more than seven-fold higher than mycobacterial counts after intravenous challenge. Naive Balb/c mice were immunized with BCG cell wall vaccine by the intratracheal route, by the intravenous route or by subcutaneous immunization. Four weeks later mice were challenged with live BCG by the intratracheal route. Following challenge, mycobacterial counts in the lungs of mice immunized by the intratracheal route, but not in the lungs of the mice immunized by the intravenous and subcutaneous routes, were significantly lower compared to controls. These results suggest that immunization with killed BCG by the intratracheal route imparts more effective mycobacterial intrapulmonary immunity than immunization by systemic routes.     

Immunological response of regional lymph nodes after tumor cryosurgery: experimental study in rats

Seven days after inoculation of metastasizing rat mammary tumor No. 1 into the thigh of 5-week-old female Sprague-Dawley rats, the tumor was treated cryosurgically by two-cycle freezing and by contact methods at -170 degrees C. Weights of the thymus and the spleen, histological findings of the lumbar lymph nodes, phytohemagglutinin (PHA)-induced blastogenesis of lymphocytes obtained from the lumbar lymph nodes and peripheral blood, and resistance rate to tumor rechallenge were examined 1, 3, 6, 10, and 17 week(s) after cryosurgery, with the following results: Thymus weight gradually decreased by 3 weeks after cryosurgery, while spleen weight increased by 1 week, recovering the preoperative level at 6 weeks. Paracortical hyperplasia of the lumbar lymph nodes markedly increased in 1 week and sinus histiocytosis increased after 3 weeks, both remaining at high values until 10 weeks, while germinal center hyperplasia showed a high value at 3 weeks and thereafter decreased gradually. PHA-induced blastogenesis of the lumbar lymph nodes significantly increased 1 week after cryosurgery and remained at its high value until 10 weeks. PHA-induced blastogenesis of peripheral lymphocytes showed the lowest value at 3 weeks and then significantly increased at 6 weeks. Resistance rate to rechallenge showed the lowest value at 3 weeks, reaching the highest level 10 weeks after cryosurgery. From the above results, it was suggested that anti-tumor immunity (resistance to tumor rechallenge) induced by cryosurgery was at the lowest level at 3 weeks after cryosurgery, and gradually increased starting at 6 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Escherichia coli peritonitis activates thermogenesis in brown adipose tissue: relationship to fever.

Fever is a complex and important nonspecific, host defense mechanism against infection. The generation of the heat necessary to increase body temperature may involve thermogenesis in brown adipose tissue. To investigate whether the febrile response to Escherichia coli peritonitis involves thermogenesis in brown adipose tissue, we assessed whole rat oxygen consumption and brown adipose tissue mitochondrial guanosine 5'-diphosphate binding. Non-lethal doses of E. coli, 1 x 10(6) to 1 x 10(8) colony forming units, induced a fever for greater than 8 h. In contrast, a dose of 1 x 10(9) colony forming units resulted in a progressive hypothermia culminating in death. A 48% increase in oxygen consumption (p less than 0.05) in E. coli-infected rats occurred almost immediately, preceded the development of the fever, and was sustained throughout the fever. There was a highly significant correlation (r = 0.736, p less than 0.01) between oxygen consumption and body temperature for both control and infected animals. Guanosine 5'-diphosphate binding assessed by multi-point Scatchard analysis of [3H]guanosine 5'-diphosphate binding to isolated mitochondria was increased by 45.4 +/- 7.3% at 1.75 h and by 31.9 +/- 9.0% at 3.5 h (p less than 0.05). The greater increase was during the rising phase of the fever. Unexpectedly, a lethal dose of 5 x 10(9) colony forming units of E. coli also increased guanosine 5'-diphosphate binding sites by 54.4 +/- 14.2% (p less than 0.05) despite a hypothermia of -1.71 +/- 0.29 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation of monoclonal antibodies to antigen Lyt-3.2

A hybridoma producing monoclonal antibodies (McAb) NATF9.9 (F9) was obtained from fusion of murine myeloma X63 and splenocytes of AKR mice immunized with a single intravenous injection of 5 X 10(7) thymocytes of CBA mice. F9 McAb were cytotoxic for 80% thymocytes, 10% splenocytes, 20% lymph node cells, 85% cortical and 32% medullary thymocytes of CBA, C57BL/6, BALB/c, DBA/2 and SJL but not for the cells of C58 and AKR mice. F9 McAb reacted only with T cells and did not react with B cells and EL4 thymoma cells (Thy-1.2+, Lyt-1+2-3-). The proportion of F9+ cells accounts for about 40% among T lymphocytes of the lymph nodes and spleen as tested by flow-type cytometry. Lymph node cells treated with F9 McAb plus complement completely lost their reactivity with rat anti-Lyt-2 McAb and only partly (by 30%) with anti-Lyt-1 McAb. The reactivity pattern of F9 McAb attests to their specificity for Lyt-3.2 antigen.     

Immunoregulation of experimental allergic encephalomyelitis: conditions for induction of suppressor cells and analysis of mechanism.

We determined requirements for the induction of immunoregulatory suppressor cells in experimental allergic encephalomyelitis (EAE) in Lewis rats. Pretreatment of rats with myelin basic protein (BP) in incomplete Freund's adjuvant (IFA) stimulates the proliferation of suppressor cells that localize in lymph nodes and spleen (but not thymus) and exert control over the development of clinical EAE. Dosage studies revealed that 3 X 10(7) suppressor cells can adoptively transfer suppression to syngeneic recipients. Transferred unresponsiveness wanes within 3 weeks, indicating that the suppressor cells are short-lived lymphocytes, although actively induced unresponsiveness persists for at least 8 weeks, probably as a result of continual proliferation under the influence of antigen. No evidence was obtained to suggest that antigen carry-over or blocking antibody production accounts for adoptive transfer of unresponsiveness. Suppressor cells apparently act at the inductive phase of the immune response since they had no inhibitory effect on adoptive transfer of disease by effector lymph node cells. Other mechanisms also may play a role in unresponsiveness to EAE, since rats pretreated i.v. with high dosages of soluble BP were temporarily rendered unresponsive, although suppressor cells could not be detected in these animals.