PubMed Health⌕ Search

Biomedical subjects

A Froese

Publications and source records attributed to A Froese.

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

Characterization of the proteolytic fragments of bovine colostral IgG1.

Bovine colostral IgG1 was subjected to both papain and pepsin hydrolysis. Papain digestion appeared to be optimal at pH 7.4 in the presence of 0.01 M cysteine. The molecule was split at the COOH-terminal side of the interchain disulfide bond(s), and in addition to Fab fragments, two Fc fragments, designated Fc(I) and Fc(II), were obtained. Both Fc fragments had an identical NH2-terminal sequence, but differed in m.w. by about 10,000, with Fc(II) being the smaller one. Differences were also observed in their circular dichroism (CD) spectra and in their susceptibility to carboxypeptidase hydrolysis. These results suggested that the distinguishing characteristics of the two Fc fragments resided in the COOH-terminal parts of the molecules. Pepsin hydrolysis yielded the expected F(ab')2 and pFc' fragments. This hydrolysis was found to be dependent upon substrate concentration leading to aggregate formation at IgG1 concentrations below 3%.

Animals↗
PubMed1977

Murine and rat IgE: relationships in terms of binding to cell receptors and to antibodies against rat epsilon chain.

The similarity between murine and rat IgE was examined in terms of their fixation to target cells and interaction with monospecific antibodies to rat epsilon-chain (anti-epsilon). Purified rat monoclonal IgE (IgEr) was found to block the fixation of murine reagin (IgEm) to mouse and rat skin and to rat basophilic leukemia (RBL) cells. The capacities of mouse reaginic serum (MRS), rat reaginic serum, and IgEr to inhibit the binding of radiolabeled 125I-IgEr to RBL cells were shown to be similar. These results suggest that the binding of IgE of either species occurs on the same or on adjacent receptor sites of mast cells and RBL cells. The antigenic cross-reactivity between IgEm and IgEr was established by depletion of the reaginic activity from MRS by treatment of MRS with anti-epsilon. The reaginic activity of MRS could be recovered by the addition of IgEr to anti-epsilon:IgEm complexes. From these findings it may be inferred that i) IgEm and IgEr share some antigenic determinants and ii) the regions of the immunoglobulins responsible for fixation to receptors on mast cells and RBL cells are identical or similar.

Animals↗
PubMed1976

Antisera to mast cells and the receptor for IgE.

Recent studies on the receptor for IgE on rat mast cells and rat basophilic leukemia cells have established that this receptor has a molecular weight of about 60,000 daltons and is, at least in part, a protein. However, so far no antisera, monospecific for this receptor, are available. Only antisera to mast cells have been described. Such antisera are capable of releasing histamine from mast cells, but only in the presence of complement. In most instances such antisera were not specific for mast cells only, but in some cases they were rendered specific by absorption with lymph node cells or liver cells. One report demonstrates that such an absorbed antiserum was capable of inhibiting the binding of IgE to mast cells. Moreover, it precipitated several mast cell surface components. One of these possibly was the receptor for IgE.

Animals↗
PubMed1976

Characterization of the target cell receptor for IgE. II. Polyacrylamide gel analysis of the surface IgE receptor from normal rat mast cells and from rat basophilic leukemia cells.

Purified rat peritoneal mast cells (RMC) and cultured rat basophilic leukemia (RBL) cells were surface labeled with 125I by using lactoperoxidase, incubated with unlabeled rat monoclonal IgE and subjected to solubilization by treatment with Nonidet P-40 (NP-40). With both cell types significant amounts of radioiodinated material could be specifically precipitated by a "sandwich" system consisting of rabbit anti-rat epsilon-chain and goat anti-rabbit Ig. The precipitates were dissociated with sodium dodecyl sulfate (SDS) and urea and subsequently analyzed by SDS-polyacrylamide gel electrophoresis. With RMC three radioactive bands were seen. One corresponded to IgE present on the RMC at the time of isolation. A small band migrating in the region of light chain was seen with both sepcific (anti-IgE) and control precipitates. It showed no demonstrable relationship to IgE. The major radioactive band corresponded to a m.w. of 62,000. This band was dependent upon the presence of IgE and was not found when non-IgE binding control cells were used. With RBL cells, only the IgE-dependent 62,000 dalton peak was present. Saturation of the IgE receptor sites of the RMC or RBL cells before lactoperoxidase labeling almost totally eliminated this radioactive band, indicating that cell-bound IgE rendered this membrane component inaccessible to the radiolabel. These results strongly suggest that this cellular component is identical, at least in part, with the target cell surface receptor for reaginic antibody. The data also further support the hypothesis that the neoplastic RBL cells have a normal surface receptor for IgE.

Animals↗
PubMed1976

Characterization of an antiserum specific for cell surface antigens of rat mast cells.

Rabbits were immunized with rat peritoneal mast cells (RMC) in complete Freund's adjuvant. The antisera (anti-RMC) were checked for their reactivity with RMC by intradermal skin tests in rats. The best serum was selected and absorbed with rat liver cells and rat immunoglobulins, including IgE. The absorbed serum (anti-RMCabs), as well as the anti-RMC serum, were then tested for their reactivity with RMC. Both sera were cytotoxic to RMC but only anti-RMC was cytotoxic for rat lymph node cells. Both sera gave positive reactions in rat skin, as seen by the permeability to Evan's blue dye. The binding of rat IgE to RMC was also inhibited by both sera. A control rabbit anti-rat sarcoma serum absorbed with liver cells did not show any interaction with RMC. When 125I-labeled RMC surface antigens were precipitated with anti-RMCabs and analyzed by SDS polyacrylamide gel electrophoresis, several components were observed. Among these was one with a mobility identical to that of a mast cell surface component that had previously been identified as the receptor for IgE or at least a component thereof.

Animals↗
PubMed1975

Binding parameters of the interaction between rat IgE and rat mast cell receptors.

Rat monoclonal IgE was purified by a combination of gel filtration and isoelectric focusing. The binding parameters of the IgE-target cell interaction were studied. The target cells used were normal rat peritoneal mast cells (RMC) and neoplastic rat basophilic leukocytes (RBL). BINDING assays were performed by adding different amounts of IgE to a constant cell number. A Scatchard analysis of the data indicated that both cell types have a similar affinity for rat IgE; the equilibrium constant was in the order of 10-9 M-minus 1. However, RBL have a higher number of receptor sites per cell--approximately 6 times 10-5 versus 3 times 10-5 for normal RMC. Since RMC have more than double the surface area of RBL, the data indicate a much higher receptor density on RBL.

Animals↗