Deregulation of mouse antibody-forming cells by streptococcal pyrogenic exotoxin (SPE). IV. Fractionation of a T-cell subpopulation which generates SPE-induced deregulation of anti-TNP PFC responses

Streptococcal pyrogenic exotoxin type A (scarlet fever toxin) is related to Staphylococcus aureus enterotoxin B

The nucleotide sequence of the gene encoding group A streptococcal pyrogenic exotoxin type A (SPE A) was determined by the dideoxy chain termination method. The first 30 residues of the translation product represented a hydrophobic signal peptide. The mature protein was 220 amino acids in length and had a molecular weight of 25,805. It has significant protein sequence homology with Staphylococcus aureus enterotoxin B but not with other proteins in the Dayhoff library.

Construction of hybridomas from nude mice with phenotypes of precursors of regulatory T cells. I. A model for study of development of T-cell function in immune systems

Functional helper and suppressor hybridomas were constructed from fractionated Type II NFR/nude mouse splenocytes which resemble precursors of T cells. After carrier priming with rabbit erythrocytes (RE), splenocytes from Type II NFR/nude mice were fractionated on nylon wool columns. Cells from two distinct fractions (Pool 1 and Pool 2) were fused with BW5147 lymphoma cells. Hybrids were selected in HAT medium and subsequently cloned. Three hybridomas constructed using Pool 1 splenocytes were capable of complementing nude mouse PFC responses to the trinitrophenyl group (TNP) of TNP-RE. Four hybridomas constructed using Pool 2 splenocytes were observed to suppress anti-TNP PFC responses. These hybridomas express the T-cell surface markers TLa, Thy 1, Lyt 1, Lyt 2 in patterns which suggest that they represent expanded clones of T cells from precursors that are arrested in their development. They appear to be blocked short of development of carrier specificity in their functional phenotypes as regulatory T cells.

Alteration of murine immune response by Pseudomonas aeruginosa exotoxin A

Pseudomonas exotoxin A has been implicated as a possible virulence factor in Pseudomonas infections. This toxin has a direct cytotoxic effect on a number of cell types, including macrophages and their precursors, and therefore may affect other cells of the immune system. NFR/N(H-2q) (+/nu or nu/nu) mice were immunized with either T-dependent or T-independent antigens along with various doses of exotoxin A. The immune response was then assayed by a modification of the Jerne plaque assay. Exotoxin A induced a dose-dependent suppression of the in vitro and in vivo immune responses to T-dependent and T-independent antigens in immunocompetent +/nu mice. However, in NFR/N nu/nu mice, suppression of the immune response to the T-independent antigen trinitrophenylated-Ficoll was not observed. Instead, a marked enhancement of the response was observed at doses of 100 and 10 ng of exotoxin A. Removal of T-cells with anti-Thy 1.2 antiserum plus complement before antigen and exotoxin A stimulation in +/nu mice results in abrogation of the suppression. These data suggest that Pseudomonas exotoxin A exerts an effect on both B- and T-lymphocyte populations to modulate the immune response and that this activity may be one facet of the pathogenic effects of this toxin.

Polyclonal antibody-forming cell activation and immunomodulation of the in vitro immune response induced by streptococcal extracellular products

The capacity of three different extracellular streptococcal products to induce polyclonal activation of precursors of plaque-forming cells (PFC) was investigated. The gamma fraction (pI = 4.2), previously shown to be only weakly mitogenic, was the most potent activator of rabbit and mouse immunoglobulin-secreting cells. The polyclonal stimulation induced by the two other fractions (kappa: pI = 4.8 and epsilon: pI = 10.3), shown to be mitogenic in both systems, was only observed in the rabbit system. Using these fractions, the in vitro immunomodulation of the anti-sheep red blood cell immune response was also investigated. Both gamma and epsilon fractions were shown to possess adjuvant properties, whereas the kappa fraction was a suppressor of the specific immune response. It appears, therefore, that the diversified immunological activities observed with extracellular streptococcal products can be dissociated and belong to different entities.