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B Merchant

Publications and source records attributed to B Merchant.

At least 55 records · Page 3Linked to original sources
PubMed1978

Fetal human hemolytic plaque-forming cells. Evidence of reactivity to maternal and other erythrocytes.

Lymphoid tissues from 24 human fetuses were assayed for hemolytic plaque-forming cells (PFC) against a variety of erythrocyte targets. PFC against maternal and other erythrocyte antigens were commonly detected in human fetal liver, lymph nodes, spleen, or thymus as early as 16 weeks gestation and were usually more abundant in liver than in spleen after 16 weeks gestation. These data corroborate studies from other laboratories which indicate that human fetuses develop some forms of immunocompetence very early during gestation.

Aging↗
PubMed1978

Effects of cyclophosphamide on the in vivo response of outbred athymic (nude) mice to a thymus-independent antigen (DNP-AGG-Ficoll).

Both nude mice (nu/nu) and their heterozygous littermates (nu/+) were injected with a single IP dose of 300 mg cyclophosphamide (CY)/kg. CY is a known immunosuppressive agent, which affects primarily B lymphocytes. Immunization with the thymus independent antigen DNP-AGG59-Ficoll after CY treatment disclosed that restoration of the primary direct PFC response occurred more rapidly in nude mice than in nu/+ mice. However in these same experiments, the primary indirect PFC response, recovered earlier in nu/+ mice than in nude mice. After CY treatment, secondary indirect PFC responses were delayed in both nude and nu/+ mice, but the greatest effect was seen in nude mice. The data suggest that the presence of T cells has little if any influence on the recovery capacity of those B cells which are destined to become direct PFC. However the recovery of B cells which are destined to produce indirect PFC responses is facilitated by the presence of T cells.

Animals↗
PubMed1978

Specificity of murine delayed-type hypersensitivity to conjugates of large or small haptens on protein carriers bearing lipid groups.

Delayed-type hypersensitivity (DH) in the mouse was provoked with different hapten-carrier complexes mixed with the cationic, surface-active lipid, dimethyl dioctadecyl ammonium bromide (DDA). DH was measured as footpad swelling. Conjugates of bovine serum albumin (BSA) with the small haptens dinitrophenyl (DNP), 'arsonate' (ARS) and 'sulphonate' (SULPH) served to generate strong DH reactions towards the homologous antigen. Insertion of a tripeptide spacer between the hapten and carrier resulted in lower DH reactivity. Optimal dosages and optimal time intervals between sensitization and DH elicitation were determined for the enlarged hapten-carrier complexes. Cyclophosphamide (CY) treatment, before priming with complexes mixed with DDA, caused a 5-6 day delay in the expression of DH but failed to evoke enhanced DH for any of the antigens tested. A broad array of cross reactions between small and enlarged hapten-carrier complexes showed a relative lack of specificity in these DH responses. The results are compared with others reported in the literature and are explained mainly by the effects of electrostatically bound lipid groups of DDA in the sensitizing conjugates.

Animals↗
PubMed1977

Hapten-specific hemolytic plaque assays usually fail to detect most of the diversity in the anti-hapten response.

Immunization of rabbits or mice with a single, chemically defined hapten elicits populations of plaque-forming cells (PFC) detectable not only on sheep erythrocytes (SRBC) bearing the immunizing hapten, but also on SRBC bearing structural analogues of the immunizing hapten. Most of these analogue-reactive PFC preferentially lyse analogue-conjugated SRBC and cannot be detected on erythrocytes bearing the immunizing hapten. Thus, they represent heretofore largely unstudied components of the secretory B-cell response to haptenic immunization, and they have been termed alloreactive PFC. Such alloreactive PFC are detectable using either classical small haptens or tripeptide-enlarged counterparts of these classical haptens. They are present in large numbers both in direct and in indirect PFC assays, and they are elicited in response to both thymic-dependent and thymic-independent antigens. Relatively few alloreactive PFC can be attributed to cells producing hapten-carrier or "bridge area"-specific antibodies. Since the antibodies released by alloreactive PFC can also be detected by passive hemagglutination, their presence does not appear attributable to vagaries of complement activation. Numerous coexisting alloreactive PFC populations are detectable after haptenic immunization. In early direct PFC responses it is not nucommon for a single alloreactive PFC population to outnumber the population of PFC detectable on SRBC bearing the actual immunizing hapten. These alloreactive PFC may be the source of at least some of the new "nonspecific" Ig which is formed at the time of immunization but about which little is known for lack of available techniques. Some possible implications of these findings on the specificity of B precursor cell activation are discussed.

Animals↗
PubMed1977

The effects of synthetic polymeric agents on immune responses of nude mice.

The influence of synthetic polymeric agents on the immune responsiveness of congenitally athymic (nude) mice was investigated by determining the effects of in vivo treatment with polynucleotides and polymeric haptenated antigens on splenic theta-bearing cells, on mitogen stimulation and on plaque-forming cell responses to thymic dependent and thymic independent antigens. Contrary to in vitro data, no evidence was obtained to demonstrate in vivo restoration of these immune parameters by the use of non-specific immune enhancers. Further, despite the continued release of lipopolysaccharide from the bowel, older nude mice (10 months old) demonstrated no acquisition of improved T-cell function. Nude mice responded well to the thymic independent antigen p-azobenzenearsonate-N-acetyl-tyrosylglycylglycine (A-TGG) Ficoll. Finally, the class specific responses to the thymic independent antigen DNP-Ficoll were significantly different from those of nu/+ littermate controls, indicating the importance of thymic influences upon the class switching of immunoglobulin responses.

Age Factors↗
PubMed1976

Contrasting effects of BCG on spleen and lymph node antibody responses in nude and normal mice.

Subcutaneous footpad injection of BCG causes a marked augmentation of popliteal lymph node plaque-forming cell (PFC) responses to DNP-derivatized hemocyanin and to sheep red blood cells, both T-dependent antigens, but not to DNP-derivatized Ficoll, a T-independent antigen. This augmentative effect occurs in normal thymus-bearing heterozygous (nu/+) mice, but not in congenitally athymic nude mice (nu/nu). In contrast, intravenous injection of BCG causes a suppressed splenic PFC response to subsequently administered T-dependent or T-independent antigens in both nude and nu/+ mice. BCG's augmenting effect on the lymph node appears to be mediated by a T-helper cell. BCG's suppressive effect in the spleen is not attributable to T cells. The actual mechanism of the BCG-mediated suppressive splenic effect remains incompletely defined at present.

Animals↗
PubMed1970

Duplicate plating of immune cell products: analysis of globulin class secretion by single cells.

Antibodies secreted by individual immune cells were collected focally in very thin "original" and "imprint" layers of agar containing the target antigen, sheep erythrocytes. Identical treatment of both layers led to mirror image patterns of hemolytic plaques. Development of one layer for immunoglobulin M hemolysins and the other for immunoglobulin G hemolysins produced unrelated plaque patterns indicating that few, if any, cells simultaneously release substantial amounts of both gammaM and gammaG antibodies.

Animals↗