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Biomedical subjects

D Boraschi

Publications and source records attributed to D Boraschi.

124 records · Page 7Linked to original sources
PubMed1980

Defective tumoricidal capacity of macrophages from P/J mice: characterization of the macrophage cytotoxic defect after in vivo and in vitro activation stimuli.

Unlike macrophages from responsive mouse strains, peritoneal cells of P/J mice treated in vivo with viable Mycobacterium bovis, strain BCG, or killed Corynebacterium parvum fail to develop tumoricidal activity. P/J macrophages treated in vitro with lymphokine-rich supernatants, bacterial endotoxic lipopolysaccharides (LPS) or T cell mitogens also fail to develop cytotoxic activity. Experimental manipulation of effector:target cell ratios, doses of activation stimuli, or tumor target cells did not evoke cytotoxic activity. The macrophage defect of P/J mice appeared similar to that of lipid A-insensitive C3H/HeJ mice. The macrophage defect of C3H/HeJ mice is controlled by a gene identical or closely linked to the Lpsd gene. Tumoricidal defects of P/J macrophages, however, appeared independent of the Lpsd gene: responses of P/J spleen cells or macrophages to LPS, which are controlled by the Lps gene, were normal. P/J mice therefore represent a distinct and potentially useful genetic probe for characterization of mechanisms in macrophage activation.

Animals↗
PubMed1979

Defective tumoricidal capacity of macrophages from A/J mice. I. Characterization of the macrophage cytotoxic defect after in vivo and in vitro activation stimuli.

Macrophages from A/J mice fail to develop tumoricidal activity after any of several in vivo or in vitro treatments that activate cells from C3H/HeN mice. Peritoneal macrophages from A/J mice treated i.p. with viable Mycobacterium bovis, strain BCG, killed Corynebacterium parvum, or pyran copolymer fail to develop in vitro tumoricidal activity; varying the numbers of macrophages from treated mice added to target cells, or the dose and time of treatment, or the treatment schedule of these in vivo activation stimuli did not evoke cytotoxic activity. Moreover, cytotoxic activity by macrophages from A/J mice was not observed with any of four target cell lines derived from three different mouse strains. In vitro treatment of peritoneal exudate macrophages from A/J mice with lymphokine-rich supernatants, bacterial endotoxins, or T cell mitogens was also ineffective; varying the numbers of treated macrophages added to target cells, the dose of in vitro activation stimuli, or the time of treatment did not evoke cytotoxic activity. Thus, A/J mice exhibit a profound defect in macrophage tumoricidal capacity to both in vivo and in vitro activation stimuli over a wide range of experimental conditions.

Animals↗
PubMed1977

Effects of whole-body irradiation on antibody affinity.

Mice exposed to a sublethal dose of X-rays were immunized with alum-precipitated DNP-KLH (dinitrophenyl-keyhole limpet haemocyanin) and B. pertussis either before or after irradiation. The primary anti-DNP antibody response was evaluated during 8 weeks after immunization by the equilibrium dialysis technique using ammonium sulphate- precipitated serum globulins and the ligand 3H-labelled xi-DNP-L-Lysine. The serum concentrations of antibody sites in mice immunized 1-5 days before or 2 h-8 weeks after 450 rad were below the values in unirradiated controls at all bleeding times. Antibody affinity, however, was found to be up to 20 fold higher in irradiated mice than in control mice when antigen was injected before, or 3-8 weeks after, irradiation. Spleen cells from mice exposed to 450 rad 1-9 weeks before killing were stimulated in vitro with PHA, ConA, or LPS. Recovery profiles of mitotic responsiveness suggest that enhancement of antibody affinity in irradiated mice could result from relative lack of suppressor T Cells.

Animals↗
PubMedDate not supplied

T cell independent induction of antigen specific suppression of the antibody response.

Immune spleen cells (from mice given 2 x 10(7) HRBC 14 days earlier) when mixed in vitro with carrier-primed syngeneic spleen cells (from mice given 2 x 10(5) HRBC 3 days earlier) are able to suppress the anti-TNP and anti-HRBC PFC response to TNP-HRBC. If immune thymocytes are substituted for spleen cells suppression is not observed. This suppression is antigen specific, resistant to anti-T treatment or x-irradiation, and is exerted by nylon wool-retained cells of the immune spleen cell population. An antigen specific suppressive factor is released from immune spleen cells in culture. Under these experimental conditions, suppression appears to be mediated by a specific product of B rather than T cells present in the immune spleen cell population.

Animals↗
PubMedDate not supplied

Antibody-dependent cell-mediated antibacterial activity of intestinal lymphocytes with secretory IgA.

Secretory antibodies of the IgA class (sIgA) are thought to have an important role in the defence against bacteria at mucosal surfaces--the level at which the infectious agents first come into contact with the host. However, the mechanism by which sIgA exert their antibacterial activity is still a matter of debate. After the recent discovery of receptors for the Fc portion of IgA (RFc alpha) on lymphocytes, monocytes and granulocytes of human, rabbit, guinea pig and mouse origin, it has been hypothesized that IgA also mediate antibody-dependent cellular cytotoxicity (ADCC). Indeed, ADCC mediated by human leukocytes against bacteria has been demonstrated in the presence of human circulating IgA. As RFc alpha have also been shown to bind sIgA, we decided to investigate whether sIgA could mediate antibacterial ADCC when bound to lymphocytes from the murine gut-associated lymphoid tissues (GALT) which first interact with the invading bacteria. By using Shigella X16 (a hybrid strain between the enteric pathogen Shigella flexneri and Escherichia coli) as target in an in vitro assay that measures cell-mediated antibacterial responses, we found that murine lymphocytes from GALT but not from other tissues are able to exert natural antibacterial activity against Shigella X16, and that sIgA significantly and specifically increase the natural antibacterial activity of GALT lymphocytes from mice and induce antibacterial activity in cells from the spleen, but not from the thymus or popliteal lymph nodes. Thus, we now propose a new role for sIgA in protecting the host against infectious agents at the mucosal level.

Animals↗
PubMedDate not supplied

Neutrophil apoptosis in autoimmune Fas-defective MRL lpr/lpr mice.

The apoptosis-defective lpr (fas) mutation in MRL mice causes the early onset of a lupus-like autoimmune disease with concomitant inflammation. In order to analyse the consequences of the impaired Fas-dependent apoptosis on inflammation, the susceptibility to apoptosis of polymorphonuclear leukocytes (PMN), obtained from MRL lpr/lpr mice, has been studied. Peritoneal PMN from lpr/lpr and control (+/+) mice were recruited with a mild inflammatory stimulus. The number of cells collected from the peritoneal cavity of young lpr/lpr mice was comparable to that obtained from age-matched control mice, indicating that PMN homeostasis is maintained regardless of the loss-of-function Fas mutation. Recruited neutrophils were exposed in culture to apoptosis-inducing stimuli. Treatment with agonist anti-Fas antibody increased apoptosis of +/+ PMN, but did not affect lpr/lpr PMN which do not express Fas on their surface. However, lpr/lpr PMN could undergo both spontaneous and stimulus-induced apoptosis in a fashion comparable to or higher than that of control +/+ mice. Analysis of mRNA expression revealed that lpr/lpr PMN have reduced expression of IL-18, whereas IL-1beta, IFNgamma, caspase 1 and caspase 3 are expressed at levels comparable to those of +/+ cells. However, caspase-3-like activity was higher in PMN from lpr/lpr mice than in +/+ cells, and correlated with enhanced apoptosis. It could be concluded that in young, uncompromised lpr/lpr mice, PMN homeostasis is still fully regulated through the involvement of Fas-independent, compensatory, apoptotic mechanisms. This could include an increased participation of caspase 3 in the apoptotic pathway, consequent to enhanced activation of the enzyme and to the decreased production of IL-18, which acts as a competitive caspase 3 substrate.

Animals↗
PubMedDate not supplied

Mechanism of acute toxicity of IL-1 beta in mice.

Human recombinant IL-1 beta was able to kill C3H/HeJ mice only when inoculated intravenously at very high doses. IL-1 beta, inoculated at 100 mg/kg i.v. as a bolus, induced a shock-like state characterized by anorexia, severe hypothermia and hypoglycemia and persistent neutrophilia, leading to death in 55% of animals generally between 24 and 48 h. In contrast, the noninflammatory adjuvant IL-1 beta peptide VQGEESNDK (position 163-171) did not induce any toxic effect in vivo, when administered following the same schedule. At variance with what was previously observed in endotoxin induced shock, IL-1 beta induced death was not preceded by appearance of circulating TNF. On the other hand, very high and persistent levels of circulating IL-6 could be detected after lethal IL-1 beta administration. Treatment of mice with ibuprofen or with chlorpromazine, both known to counteract some of the toxic effects of IL-1 in vivo, could protect from IL-1 beta induced mortality. Both drugs, at doses protecting from IL-1 beta induced death, were able to abolish IL-1 beta-induced rise of circulating phospholipase A2 (PLA2) activity, and the subsequent generation of toxic PLA2-derived metabolites.

Amino Acid Sequence↗
PubMedDate not supplied

Defining the structural requirements of a biologically active domain of human IL-1 beta.

The immunostimulatory activity in vivo of the pleiotropic cytokine IL-1 beta can be retained by its nonapeptide VQGEESNDK, in position 163-171. A series of shorter and longer peptides around this position has been assayed for IL-1-like biological activity, in order to identify the structural requirements for full expression of adjuvant capacity. Elongated peptides, comprising the loop region 165-169 and up to six amino acids in the preceding beta strand or up to seven amino acids in the following beta strand, showed activity comparable or lower than that of the nonapeptide 163-171. This would indicate that the beta strand sequences are not required for optimizing the active conformation of the immunostimulatory IL-1 beta moiety. Accordingly, stabilization of the 163-171 peptide conformation by cyclization did not increase its biological activity. In contrast, the pentapeptide GEESN, corresponding the exposed loop 165-169 between two beta strands, had biological activity higher than that of the 163-171 nonapeptide and fully comparable to that of the entire IL-1 beta protein. Thus, the highly exposed fragment 165-169 within the IL-1 beta molecule may be the structure selectively responsible for the IL-1 beta immunostimulatory capacity in vivo.

Adjuvants, Immunologic↗
PubMedDate not supplied

Peyer's patch lymphocytes express natural cytotoxicity but not natural killer activity.

The distribution of natural cytotoxic (NC) cells in the gut-associated lymphoid tissues (GALT) and in peripheric lymphoid organs was analyzed in comparison to that of natural killer (NK) cells. It was found that cells from the intestinal epithelium, mesenteric lymph nodes and spleen possess significant levels of NC and NK activity, whereas in thymus and popliteal lymph nodes both the natural activities are negligible. As previously shown for splenocytes, the NC activity of GALT cells is detectable in the 16-hour assays and not in the 4-hour assays. Interestingly, Peyer patches lymphocytes (PPL) possess extremely high NC activity but no NK activity. The NC activity of PPL is still high in NK-deficient mouse strains such as A/J and SJL/J. To further support the observation that the effector PPL are truly NC cells, it was shown that, as previously reported for spleen NC activity, overnight incubation at 37 degrees C of the lymphocytes only marginally affected the cytotoxicity of PPL, which could in turn be augmented by interleukin-3 (IL-3) containing supernatants. On the contrary, IL-2 could not increase NC or NK activity by PPL whilst augmenting NK activity of splenocytes. Thus, for the first time a cell population is identified which expresses only NC activity and not NK and which can be positively regulated only by IL-3.

Animals↗