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A M Faria

Publications and source records attributed to A M Faria.

11 recordsLinked to original sources
PubMed1998

Aging and immunoglobulin isotype patterns in oral tolerance.

In the present review we address oral tolerance as an important biological phenomenon and discuss how it is affected by aging. Other factors such as frequency of feeding and previous digestion of the antigen also seem to influence the establishment of oral tolerance. We also analyze immunoglobulin isotypes of specific antibodies formed by tolerant and immunized animals of different ages submitted to different conditions of oral antigen administration. Isotypic patterns were studied as a parameter for assessing the pathways of B and T cell interactions leading to antibody production.

Aging↗
PubMed1998

Interruption of recently induced immune responses by oral administration of antigen.

Interest in oral tolerance has been renewed in the last few years as a possibility of intervention in human autoimmune diseases. An obstacle in this direction is that, although easily induced in animals virgin of contact with the antigen, oral tolerance becomes hard to induce in previously immunized animals. The present results show that there is an early period after primary immunization in which prolonged oral exposure to the antigen may arrest ongoing immune responses. Beyond this period, oral exposures to the antigen become ineffective and may actually boost immune responses. The end of the susceptible period coincides with the emergence of free specific antibodies in serum. However, the previous administration of purified anti-ovalbumin antibodies (40 micrograms) was unable to block the induction of oral tolerance to ovalbumin in normal mice.

Administration, Oral↗
PubMed1998

Oral tolerance induction with altered forms of ovalbumin.

As a T cell-dependent phenomenon, oral tolerance is not expected to depend necessarily on native configuration of antigens. We investigated the induction of oral tolerance with modified ovalbumin (Ova). Oral administration of heat-denatured (HD-Ova) and cyanogen bromide-degraded ovalbumin was less effective than native Ova in inducing oral tolerance in B6D2F1 mice. HD-Ova was effective in suppressing delayed-type hypersensitivity (DTH) reactions but did not suppress specific antibody formation. Injection of Ova directly into the stomach, but not into the ileum or cecum, suppressed subsequent immunization to DTH reactions. Gavage with protease inhibitors (aprotinin or ovomucoid) before gavage with Ova was ineffective in blocking tolerance induction. Treatment with hydroxyurea to destroy cycling cells 24 h before gavage with Ova blocked oral tolerance induction and also the possibility to passively transfer tolerance to naive recipients with the serum of mice gavaged with Ova 1 h before. The implications of these findings about oral tolerance induction are discussed.

Administration, Oral↗
PubMed1997

Immaturity, ageing and oral tolerance.

Founding studies of cellular immunology emphasized that tolerance to allografts could only be achieved early in the embryonic or neonatal period, suggesting that the establishment of self-tolerance, a main event in the organization of the immune system, would necessarily take place in immature hosts. Contradicting these ideas, oral tolerance is a common, daily phenomenon, easily achieved by a physiological route in adult immunocompetent animals. Furthermore, there is solid evidence that, after the neonatal period, the susceptibility to oral tolerance induction also wanes and that it may be restored by adoptive transfer of cells from young hosts. These findings are briefly reviewed here to emphasize that immunological activity is a continuous and ongoing epigenesis extending throughout the entire life of the organism, far beyond the early phases of ontogenesis.

Aging↗
PubMed1993

Systemic immunization of mature mice by the oral route.

1. Mice of several strains which are susceptible to the induction of oral tolerance by a single gavage with 20 mg of ovalbumin (Ova) when young adults (7-8 weeks old) become less susceptible or refractory to tolerance induction when mature (20-40 weeks old). The antibody-forming capacity of these mature animals remains invariant compared to young adults (8-10 weeks old). 2. Mature mice of several strains display significant serum antibody responses to 3 gavages (days 0, 7 and 28) with Ova; as assessed by ELISA titers, these responses are similar in magnitude to those elicited by standard ip immunization with small doses of Ova. 3. In mature H-III mice, gavages on days 0, 7 and 28 induced significant antibody formation. On the contrary, the ingestion of the same amounts of Ova on days 0, 7 and 28 induced oral tolerance. Concomitant gavage with saline on the days of Ova ingestion failed to inhibit tolerance induction. 4. In H-III mice displaying circulating antibodies induced by repeated gavage with Ova, additional ip injections of Ova failed to increase the antibody titers.

Administration, Oral↗
PubMed1993

Decrease in susceptibility to oral tolerance induction and occurrence of oral immunization to ovalbumin in 20-38-week-old mice. The effect of interval between oral exposures and rate of antigen intake in the oral immunization.

Maturation into adulthood, from 8 to 24 weeks of age, significantly influences the induction of oral tolerance in different strains of mice. Animals from strains which are susceptible to the induction of oral tolerance to ovalbumin (OVA) at 8 weeks of age become refractory at 24 weeks of age. Furthermore, in several strains, intermittent exposure to OVA exclusively by gavage resulted in high titres of circulating anti-OVA antibodies. However, the voluntary intake of similar doses of OVA at the same intervals failed to immunize mice of one of the most responsive strains, H-III.

Administration, Oral↗
PubMed1992

T560: an (H-2b x H-2a) F1 hybrid, phosphorylcholine (PC)-binding, murine B cell lymphoma that bears receptors for IgA and IgG, presents antigen and secretes IL-4.

We describe T560, a tissue culture-adapted B lymphoma derived from the gut-associated lymphoid tissue (GALT) of a (B10 x B10.H-2a H-4b)F1 hybrid mouse. This lymphoma is interesting and useful not only because it bears an unusual IgA receptor, fully described elsewhere, but also because it is potentially capable of presenting antigen to T cells restricted by the MHC of either parent. Here we document that T560 cells are IgG2a kappa +, Ia+, B220+, J11d.2+, CD3-, CD4-, CD5-, Mac 1-, Mac 2-, non-specific esterase-. They bind bromelain-treated mouse RBC (BrMRBC) in a PC chloride-inhibitable manner but do not bind SRBC, ox RBC (ORBC) or TNP-ORBC. Two lines, T560.1 and T560.2, and several clones are available. T560.1 and its clones contain low numbers of IgA rosette-forming cells (RFC), intermediate numbers of IgG2a RFC and moderately high numbers of IgG2b RFC; T560.2 and its clones contain moderately high numbers of IgA RFC and low numbers of both IgG2a and IgG2b RFC. Both lines stimulate both B10 and B10.A cells in mixed lymphocyte reactions (MLR) and present keyhole limpet hemocyanin (KLH) to KLH-reactive T cells. T560.2 populations are, however, more efficient possibly because they have somewhat higher proportions of brightly fluorescent Ia+ cells and secrete larger quantities of lymphokine than T560.1 cells. They present PC-conjugated KLH (PC-KLH) approximately 20 times more efficiently than unconjugated KLH, suggesting that their PC binding receptors function in antigen uptake. They constitutively produce IL-1, IL-4 and IL-6, but not IL-2, IL-5 or TGF beta. Neither their IgA nor their IgG receptor expression is affected by IL-4 or by IFNs-alpha, -beta, or -gamma. In their ability to bind BrMRBC and secrete IL-4, they resemble the CH12 lymphoma but differ from it in that they are of F1 hybrid origin, are CD5-, bear IgG2a rather than IgM, do not bind sheep erythrocytes and have a receptor for IgA not present on CH12.

Animals↗
PubMed1991

Sensitivity of receptors for IgA on T560, a murine B lymphoma, to phorbol myristate acetate and to phosphatidylinositol-specific phospholipase C.

A GALT-derived B lymphoma, T560, that bears IgAR is described. T560 is IgG2a kappa +, Ia+, B220+, J11d+, Thy-1-, CD3-, CD4-, CD5-, Mac 1-, Mac 2-, nonspecific esterase negative and binds bromelain-treated mouse RBC but not SRBC or ORBC. It presents antigen, secretes IL-1, IL-4 and IL-6 but not IL-2, IL-5 or TGF beta and appears to be related to the Lyt 1+(CD5) lineage of B cells though it lacks Lyt 1. T560 bears IgAR that, on the cell surface, are completely cross-inhibited by low concentrations of IgM and by high concentrations of IgG2a and IgG2b. They do not appear to represent a cell-surface form of galactosyl transferase. They are inducible by high concentrations of IgA, sensitive to trypsin and insensitive to neuraminidase. They are down-regulated by activation of PKC with PMA, but their recovery is not inhibited by cycloheximide, indicating that they are not degraded or shed. They may either lose their affinity for IgA or be internalized without degradation. Seventy percent of IgA receptor activity is lost when T560 is treated with PI-PLC; part of this loss of activity is due to activation of PKC and is inhibited by staurosporine, but approximately 30% of it is not protected by staurosporine indicating that some, or all, of the IgA receptor of T560 is connected to the cell membrane via a GPI linker. The T560 IgA receptor could be related to the poly-Ig or M cell receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Tolerance induction and immunological priming initiated by mucosal contacts with protein antigens in inbred strains of mice.

1. We show that mouse strains differ widely in susceptibility to tolerance induction and/or immunization (priming) following contact of protein antigens (ovalbumin, human or bovine gamma globulins) with different mucosal surfaces. 2. When compared to a control group pretreated with saline, mice pretreated by the oral (intragastric) route with antigen became significantly less responsive to subsequent parenteral immunization (i.e., tolerant). This was observed in most, but not all, antigen/strain combinations. 3. Similar, although less prominent changes were induced by pretreatments with antigen by the ocular (conjunctival) route. 4. No significant effects were observed following pretreatments by the nasal, vaginal or rectal routes. 5. Genes present in strains selected for multispecific "high" or "low" responsiveness are included among those involved in tolerance induction following mucosal contacts with protein antigens.

Animals↗