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Biomedical subjects

M Campa

Publications and source records attributed to M Campa.

At least 91 records · Page 5Linked to original sources
PubMed1979

Depression of the antibody response in Pseudomonas aeruginosa-injected mice.

Heat-killed Pseudomonas aeruginosa inhibit antibody response in C57BL/6 mice. The depression of this response is dependent on the dose of bacteria injected, on the time interval between microorganism injection and antigen administration, and on the nature of the antigen used. Cell transfer experiments provide evidence that suppressor cells are not operative in this model. Furthermore, the results show that P. aeruginosa induces a marked dose-dependent proliferation of spleen cells in vivo, and the in vitro targets of this proliferative effect are B lymphocytes. It is suggested that whole, heat-killed P. aeruginosa in vivo also behave as cell mitogens on B lymphocytes which, when strongly stimulated to proliferate, temporarily lose their capacity to mount a normal antibody response.

Animals↗
PubMed1979

Depression of contact sensitivity by Pseudomonas aeruginosa-induced suppressor cells which affect the induction phase of immune response.

The cellular basis of depression of contact sensitivity to oxazolone in mice injected with Pseudomonas aeruginosa was studied. Cells from draining lymph nodes of mice sensitized with oxazolone 18 h previously were able to induce contact sensitivity to normal mice when administered in their footpads. In contrast, cells from draining lymph nodes of P. aeruginosa-injected and oxazolone-sensitized donors failed to induce contact sensitivity when injected in the footpad of normal mice and were capable of actively blocking the immunizing process brought about by lymph node cells from sensitized mice when injected together in the footpad of normal recipients. The P. aeruginosa-induced suppressor cells required antigenic stimulation, had precursors sensitive to cyclophosphamide, and did not affect the effector mechanisms of contact sensitivity. Thus, the results suggest that P. aeurginosa depresses contact sensitivity to oxazolone by enhancing the activity of suppressor cells which normally arise during the sensitization process and which affect the afferent limb of the immune response, probably by inhibiting the normal recruitment of T lymphocytes in the draining lymph nodes.

Animals↗
PubMed1978

An analysis of the role of lymphatic leukemia virus in the immunodepression exerted by Friend complex in leukaemia-resistant C57BL/6 mice.

Leukaemia-resistant C57BL/6 mice inoculated with the Friend complex (FLC) present a transient but definite depression of the ability to develop IgM and IgG antibody-producing cells to sheep red cells (SRC). In this paper it is shown that this immunodepression cannot be attributed solely to the lymphatic leukaemia virus (LLV) component of FLC which is immunodepressive in susceptible mice. This conclusion was reached by investigating the immunological reactivity of C57BL/6 mice following inoculation with two isolates of LLV. Circumstantial evidence obtained by examining the replication of FLC and LLV, the antibody response to E. coli lipopolysaccharide (LPS) and the ability of syngeneic macrophages administered together with the antigen to restore the response to SRC points to the same conclusion. There were also indications that the low sensitivity to depression by viruses of the Friend complex exhibited by the anti-LPS antibody response is due to the mitogenic activity of this antigen.

Animals↗
PubMed1978

Depression of contact sensitivity by enhancement of suppressor cell activity in Pseudomonas aeruginosa-injected mice.

Heat-killed Pseudomonas aeruginosa depresses contact sensitivity to oxazolone in C56BL/6 mice. The draining lymph nodes and spleens of mice exhibiting an impaired reactivity to oxazolone contain a cell population capable of depressing the response to oxazolone of recipients sensitized immediately before cell transfer. The suppressive activity of these cells appears to be antigen specific, since they do not affect the response to picryl chloride and because they do not arise in P. aeruginosa-injected but not oxazolone-sensitized mice. These suppressor cells occur in the draining lymph nodes and spleen at 3 and 4 days after sensitization, respectively, and have precursors sensitive to cyclophosphamide. It is concluded that P. aeruginosa depresses contact sensitivity to oxazolone by enhancing the suppressor cell activity of the regulatory cells which arise during conventional sensitization.

Animals↗
PubMed1976

[Salmonella strains recently widespread in Italy and its sensitivity to some common antibiotics (author's transl)].

A study has been carried out in order to evaluate the sensitivity of a group of some 517 strains of salmonella identified by the Pathogenic Enterobacteria Centre of Central Italy in the biennium 1974-75 to various antibiotics and chemotherapeutic agents. As far as the average percentage of sensitivity to the drugs by the strains tested is concerned, the results obtained are indicative of a situation which may be optimistically looked upon as far as our regions are concerned. Some widely used drugs such as chloramphenicol, ampicillin, streptomycin and kanamycin showed a high percentage of activity in vitro towards Salmonellae with the exception of S. wien, whereas gentamicin, co-trimoxazole, nalidixic acid, furoxone and cephradine were more widely active, No substantial differences were found between strains normally present in our regions which are, at present, characterized by a stationary epidemiological situation (S. typhi, S. paratyphi B, S. enteritidis, S. typhi-murium) and sertypes which, having been present in Italy for a long time, appear today to have an increasing diffusion (S. infantis, S. newport, S blockley and S. thompson). As for the Salmonellae of recent appearance and diffusion in Italy (S. panama, S. agona, S. wien) a more resistant pattern of behaviour to various drugs was found; this was particularly remarkable for S. wien which is the last in order of appearance in our population. Finally, the probable reasons for this difference in behaviour are discussed in view of our present knowledge on drug-resistance and on the role played by antibiotics as selective agents at an environmental level.

Animals↗
PubMed1976

Evidence for suppressor cell activity associated with depression of contact sensitivity in Pseudomonas aeruginosa infected mice.

Pseudomonas aeruginosa infection depresses contact sensitivity to 2-phenyl-4-ethoximethylene-oxazolone (oxazolone), and enhances the antibody response to sheep erythrocytes (SRBC) in the mouse. Anti-oxazolone antibody titres were found not to be significantly different in infected and uninfected animals; thus, the major circulating classes of antibodies do not seem to be responsibile for the observed depression of skin reactivity. Low dose (20 mg/Kg) cyclophosphamide (CY) pretreatment induced a further potentiation of antibody response to SRBC, and prevented depression of contact sensitivity in infected mice. On the other hand, when infected animals were pretreated with high doses (200 mg/Kg) of CY, antibody production was completely suppressed, whereas contact sensitivity was unaffected. Since CY treatment is known to selectively inhibit B lymphocytes, and since it can abrogate the infection-induced depression of reactivity to oxazolone, it is suggested that suppressor cells, which may have B-cell characteristics, are stimulated during P. aeruginosa infection in the mouse.

Animals↗
PubMed1975

Immunodepression by Rowson-Parr virus in mice: effect of Rowson-Parr virus and Friend leukemia complex infections on background antibody-forming cells to various erythrocytes.

The numbers of background antibody-forming cells (BPFC) toward erythrocytes of various species present in the lymphoid organs of unimmunized susceptible BALB/c and resistant C57BL/6 mice were investigated at various times after infection with Friend leukemia complex (FLC) or Rowson-Parr virus (RPV). Both virus preparations induced an increase of BPFC numbers in both animal strains, but the rate and magnitude of the enhancements produced by RPV were much lower. The degree of potentiation varied with the specificity of the BPFC populations and was more pronounced in the spleen than in the lymph nodes and in BALB/c than in C57BL/6 mice. In the late stage of FLC infection, the numbers of splenic BPFC to some erythrocytes underwent a dramatic fall, which was not observed in RPV-infected mice. BPFC present in BALB/c splenocytes cultured in diffusion chambers implanted in the peritoneal cavity of isogeneic normal mice were not affected by viral infection of the chambers.

Animals↗
PubMed1975

Immunodepression by Rowson-Parr virus in mice: effect of Rowson-Parr virus and Friend leukemia complex infections on contact sensitivity in susceptible and resistant mice.

Contact sensitivity to 2-phenyl-4-ethoxymethilene oxazolone, as a probe for cell-mediated immunity, was investigated in susceptible BALB/c and resistant C57BL/6 mice after infection with Friend leukemia complex (FLC) or with Rowson-Parr virus (RPV). In BALB/c mice, FLC depressed contact sensitivity when given before primary sensitization but had no effect on established contact sensitivity nor on the response elicited by a booster application of the sensitizer. These findings, together with the failure to alter reactivity to an aspecific inflammatory stimulus, indicate that FLC impairs the afferent limb of the response. In the same strain of mice RPV infection did not significantly depress contact sensitivity, as judged by the extent of the reaction 24 h after challenge, but slightly inhibited the early antibody-mediated phase of this reaction. In C57BL/6 mice neither viral preparation affected contact sensitivity.

Allergens↗
PubMed1975

Depression of contact sensitivity and enhancement of antibody response in Pseudomonas aeruginosa-infected mice.

The effect of Pseudomonas aeruginosa infection on contact sensitivity to 2-phenyl-4-ethoximethylene-oxazolone (oxazolone) and on antibody response to sheep erythrocytes, horse erythrocytes, and Escherichia coli 0111:B4 lipopolysacharide was investigated in outbred C57BL/6 mice. Injection of 0.5 and 0.2 median lethal doses significantly depressed contact sensitivity to oxazolone, whereas injection of 0.5 median lethal dose of heat-killed microorganisms did not. The filtrate of a 24-h broth culture did not affect contact sensitivity as well. Antibody production against sheep erythrocytes, horse erythrocytes, and lipopolysaccharide (evaluated as plaque-forming cells and circulating hemagglutinin and hemolysin titers) was found to be significantly enhanced both in animals injected with living bacteria and in those which received heat-killed microorganisms. The simultaneous occurrence of depression of cell-mediated immunity and potentiation of humoral response suggests that P. aeruginosa might interfere at different levels of the host immunological responsiveness.

Animals↗
PubMedDate not supplied

Purine metabolism and B-lymphocyte development in the chicken bursa of fabricius.

The activity of three enzymes involved in the salvage pathway of purine nucleosides--purine nucleoside phosphorylase (PNP), xanthine dehydrogenase (XDH), and hypoxanthine-guanine phosphoribosyl transferase (HGPRT)--was investigated in cellular fractions of the chicken bursa of Fabricius differentially enriched in epithelial cells or lymphocytes. Markedly increasing levels of PNP and XDH were observed along with the enrichment in epithelial cells together with a slight, though significant, decrease in HGPRT activity. By contrast, a dramatic fall in PNP and XDH activities was detected along with the enrichment in lymphocytes together with a slight, though significant, increase in HGPRT activity. This sharply different distribution of the three enzymes, all sharing hypoxanthine as a substrate, clearly indicates that lymphocytes preferentially channel hypoxanthine into the salvage and interconversion pathways, phosphorylating it to IMP, while epithelial cells rapidly catabolize such a purine base to uric acid. Moreover, epithelial cells, unlike lymphocytes, are able to retain high intracellular levels of both hypoxanthine and inosine. These results support the possibility that epithelial cells contribute to the normal development of bursal lymphocytes by supplying such actively proliferating cells with purine rings and at the same time by preventing them from accumulating potentially toxic high levels of purine nucleotides being able to rapidly eliminate excess hypoxanthine as uric acid from the bursa environment into the bloodstream.

Animals↗
PubMedDate not supplied

Depression of the immune responsiveness in mice treated with thioacetamide after antigen exposure.

The effects of the weak carcinogen thioacetamide (TAA) on the mouse immune response have been investigated. TAA administration up to 1 day after antigen priming markedly suppressed the antibody response to both T-dependent (sheep erythrocytes) and T-independent (trinitrophenyl-Ficoll) antigens; the compound was ineffective when given 3 or 4 days after immunization. A significant suppression of the in vitro lymphoproliferative response to the B-cell mitogen S. aureus Cowan I was evident from 3 to 48 h after TAA treatment. On the other hand, cell-mediated immune response to oxazolone was suppressed by TAA at each time tested, including that of challenge. The in vitro lymphoproliferative response to concanavalin A was decreased 12 h after TAA administration only, when adenosine deaminase activity within lymphocytes was increased. Furthermore, TAA is endowed with anti-inflammatory activity, as shown by the decreased footpad swelling and by evaluation of the inflammatory cell infiltration upon carrageenan injection. Taken together, these findings suggest selective TAA interaction with multiple targets within the immune system, including B- and T-lymphocytes, while non-specific cytotoxicity can be reasonably ruled out, since hematological determinations and phenotypic analysis of spleen lymphocyte subsets showed no relevant changes.

Acetamides↗
PubMedDate not supplied

[Pseudomonas aeruginosa: immunotypes and drug resistance].

Serotyping of Pseudomonas aeruginosa by Fisher's schema has been used to study the prevalence of particular immunotypes among strains of P. aeruginosa obtained from clinical specimens. About 78% of the isolates were serotypable and about 22% were not. Immunotypes 2 and 6 turned out to be the most prevalent, whereas immunotypes 5 and 7 were the least frequent. Immunotypes 2, 5, 6 and 7 did not vary significantly as far as frequency in the various sources is concerned, with the exception of immunotype 2, which was significantly less frequent in isolates from the expectorated sputum. In such isolates immunotype 3 was significantly more frequent than in other sources, whereas immunotype 4 was significantly more frequent in isolates from the feces. It was next investigated whether a correlation exists between antibiotic susceptibility and particular immunotypes. A high percentage of the non-typable strains and of those belonging to immunotypes 2 and 6 proved to be resistant to the antimicrobial agents tested.

Humans↗