Role of C'3 and Fc receptors in B-lymphocyte activation. (17/970)

Attempts were made to identify the non-Ig lymphocyte receptor responsible for B-cell induction by antigen and polyclonal B-cell activators (PBA). As a first step, the role of C'3 and Fc receptors was analyzed. It was shown that complement could be fixed onto B cells to such an extent that the lymphocytes could not bind complement-coated red cells, but this did not result in induction of polyclonal antibody synthesis, nor did it inhibit the lymphocytes response to PBA. However, the C'3 receptros possessed a passive focussing role in the induction of polyclonal antibody responses. Thus, PBA that had fixed complement activated polyclonal responses at lower concentrations than the same substances that had not fixed complement. Most likely the dual binding of PBA molecules to B cells by the PBA and the C'3 receptors caused more PBA molecules to be bound to each cell. However, the focussing function of the C'3 receptors was several orders of magnitude smaller than that of the Ig receptors. Analogous studies were carried out with Fc receptors. Binding of different types of antigen-antibody complexes did not cause activation of polyclonal or specific antibody synthesis, nor did it significantly interfere with induction of antibody synthesis by PBA substances.  (+info)

Temperature-sensitive cell mutations that inhibit adenovirus 2 replication. (18/970)

Five temperature-sensitive growth mutants of the hamster cell line BHK-21 were tested for the ability to support adenovirus 2 multiplication at 39 degrees and 33 degrees. Wild-type BHK-21 and mutants ts 422E and ts BCH yielded comparable amounts of virus at 33 degrees and 39 degrees, whereas in three other mutants, ts T22, ts T23, and ts AF8, virus production at 39 degrees was reduced to about 1% of that at 33 degrees. Virus yield in the three mutants was not reduced because of a delay in virus production; for all cells tested maximal virus yield at 39 degrees was obtained by 40-50 hr after infection. Normal yields of infectious virus were not obtained from ts AF8 even with a very high multiplicity of infection. In contrast, the virus yield from ts T22 and ts T23 was multiplicity-dependent. Shiftup experiments demonstrated that in ts AF8, a cell cycle mutant which at 39 degrees becomes arrested in G1, virus multiplication was thermosensitive for the first 40 hr of infection. In ts T22 and ts T23, the thermosensitivity was only for the first 3-4 hr of the infection. In all three mutants viral DNA synthesis was reduced by at least 95% at the higher temperature. The cell function specified by the ts AF8 mutation seems to be required for the early period of adenovirus 2 replication, after virus entry into the cell but before the onset of viral DNA replication.  (+info)

Thymus dependence of the IgA response to sheep erythrocytes. (19/970)

The thumus dependence of the IgA response to sheep red blooc cells (SRBC) was studied by means of cell transfer experiments in mice. Only low numbers of IgM-, IgG- and IgA-plaque-forming cells (PFC) were observed in those recipients which received only spleen cells from adult thymectomized, irradiated and bone marrow-reconstituted mice (B cells). High numbers of IgM-, IgG- and IgA-PFC were observed when B cells and educated T cells were transferred to the recipients. Evidence is provided that B cells committed to IgA synthesis require the same degree of interaction with T cells as B cells committed to IgM synthesis, but a lower degree of interaction with T cells than B cells committed to IgG synthesis.  (+info)

The possible presence of a bursa-independent, IgM-producing system in chicks. (20/970)

The number of splenic plaque-forming cells significantly increased in bursectomized chicks immunized secondarily with SRBC. Further experiments using rabbit antiserum specific to the bursa of Fabricius indicate that the different types of antibody-producing cells might be engaged in the synthesis of IgM in bursectomized chicks. The possible presence of a bursa-independent, IgM-producing system in chicks is suggested.  (+info)

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. (21/970)

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.  (+info)

Heteroimmunization to the capsular polysaccharide of Haemophilus influenzae type b induced by enteric cross-reacting bacteria. (22/970)

Cross-reacting Escherichia coli strains Easter and 89 and Bacillus pumilis fed to newborn rabbits and E. coli fed to adult rhesus monkeys did not exert untoward reactions. The E. coli regularly colonized the newborns' intestinal tract from 1 to 7 weeks. High doses of E. coli were necessary to colonize adult primates. Colonization occurred in fewer newborn rabbits and lasted only 1 to 3 weeks with B. pumilis. Colonized newborn rabbits and adult rhesus had an active Haemophilus influenzae type b (HITB) immune response. In the rabbit, colonization resulted in accelerated induction of immunoglobulin (Ig) M-. IgA-, and IgG-producing cells in the spleen, mesenteric lymph nodes, and Peyer's patches after HITB challenge. E. coli-fed and control newborn primates were naturally colonized with nasopharyngeal and enteric cross-reacting bacteria and both groups rapidly developed HITB antibodies in the absence of the homologous organisms. Human newborn stool cultures, taken at the time of discharge from the nursery, showed a 0.9% carriage rate for cross-reacting E. coli. These "carrier" infants acquired HITB antibodies more rapidly than their age-matched "noncarrier" controls.  (+info)

Serotyping of Chlamydia: isolates of bovine origin. (23/970)

Chlamydial isolates of bovine origin were serotyped by a plaque reduction method. Of the two major serotypes observed, type 1 included isolates from bovine abortion and enteric infections, whereas type 2 isolates were associated with polyarthritis or encephalomyelitis. These two serotypes were identical to those with a similar disease distribution previously observed in isolates of ovine origin. The two groups did not cross-react and they were serologically unrelated to chlamydiae of avian origin. Thus, it appears that many chlamydial isolates causing intestinal infections or abortion in sheep or cattle are closely related antigenically, as are those producing polyarthritis, encephalomyelitis, and conjunctivitis, and that the two groups are distinct.  (+info)

Detection of virus-specific antibody-forming cells of mice immunized with Newcastle disease virus. (24/970)

The hemolytic plaque assay was adapted to the detection of antibodies to Newcastle disease virus (NDV) in an in vivo, an in vitro system, and a combined in vivo-in vitro system. Several conditions were tested for coupling of sheep erythrocytes to NDV and for the kinetics of plaque formation in the in vivo and in vitro systems. The one set of conditions which provided the best responses is presented. The effect of multiple injections of NDV into mice on plaque formation was optimized.  (+info)