The antral hormone gastrin has generally been regarded as a non antigenic molecule necessitating its conjugation with a large "carrier” to be an effective inducer of antibody. Such conjugation has normally taken the form of covalent binding to a highly antigenic molecule or ionic binding to an inert particle. Alternatively, some success has been achieved by the injection of impure antral extracts. This report describes four approaches to the problem of the induction of antibodies specific for gastrin. Initially, natural hog gastrin was obtained after the procedure of Gregory and Tracy (1964). The pure active hormone was modified by alkaline hydrolysis to liberate an N-terminal amino group for covalent conjugation. The modified gastrin, however, was not specifically identified or isolated in quantity. Consequently, pure and impure antral extracts, hemocyanin-bound synthetic human gastrin and latex-bound gastrin were applied to a variety of animals. Passive hemagglutination tests in ducks revealed titres of 400 to 1600 to both the pure and impure extracts but a series of four injections of pure gastrin into an antrectomized rabbit failed to raise detectable antibody. Injections of 3 mg. of SHG bound to hemocyanin was unsuccessful; antibody titre to the carrier molecule was high but no specificity appeared to be directed to the synthetic hapten. The immunization of chickens with latex-bound natural gastrin was more fruitful. Although a number of precipitin tests established the presence of antibodies to gastrin, it was apparent that the assay was inadequate as a sensitive test for the bivalent antigen. Furthermore, the antibody titre was not sufficiently high to be successfully applied to a radioimmunoassay. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

Considerable evidence indicates that events at the cell surface play a central role in the regulation of growth of normal and neoplastic cells. It is possible that modification of the surface molecules might be, in part, responsible for the processes that accompany tumorigenesis. These surface molecules are termed TSTA (tumor specific transplantation antigens) and TAA (tumor associated antigens). The purpose of this study is to raise xenogeneic antiserum which can recognize TAA. This antiserum, then, can be used as a tool to enrich or purify the antigen in question. Using the antibody feedback inhibition method which has been developed in our laboratory, an antiserum directed toward membrane components of DBA/2 mastocytoma P815 cells was raised. This antiserum was found to be specific for tumor cell extracts and had no reactivity with comparable extracts of normal cells when tested by complement fixation. This antiserum was also capable of killing P815 cells in the presence of guinea pig complement but had no reactivity with another DBA/2 tumor or a variety of normal DBA/2 cell preparations. When mixed with varying numbers of tumor cells and injected intraperitoneally into either DBA/2 or B6D2 Fl mice, the antiserum demonstrated a protective effect by either prolonging survival time or, apparently facilitating complete removal from the body of tumor cells when low numbers of cells were injected. The antiserum was used to monitor the purification of tumor associated antigen (TAA) of P815 cells. Membrane extracts of both P815 and normal DBA/2J spleen and peritoneal exudate cells were subjected to DEAE fractionation and gel filtration, following which fractions were tested for reactivity with the anti-P815 antiserum. Fractions from P815 extracts shown to be enriched for the TAA were used to raise a second antiserum specific for the tumor. This antiserum was also shown to have specificity for P815 and none for normal DBA/2J cells by ⁵¹Cr release assays in the presence of guinea pig complement and by surface labeling using peroxidase labeled sheep anti-rabbit immunoglobulin after treatment of either P815 or normal cells with the antiserum. This second antiserum (anti-P815-2), when allowed to react with ¹²⁵I-labeled TAA-enriched fractions of the P815 membrane extracts and passed over Sepharose-protein A columns, permitted the isolation of a single major component, detectable on autoradiographs of gradient acrylamide gels. This component was not present in equivalent normal DBA/2 tissue extracts, nor was it detectable when these tests were repeated using an antiserum raised against normal DBA/2 membrane preparations. It was thus concluded that this material constituted a TAA of the P815 mastocytoma. Then this major band was cut, eluted and used in CFA to immunize a rabbit. Three immunizations were needed to get antiserum which was specific to P815 cells and membrane extracts. P815 cells treated with this last antiserum were resistant to lysis by syngeneic cytotoxic cells but they were not when allogeneic cytotoxic cells were used. On the other hand, rabbit anti DBA/2 as well as mouse anti H-2d serum also blocked the syngeneic killing as well as having a blocking effect in the allogeneic killing. This suggests that this antiserum recognizes membrane molecules which are important for recognition by syngeneic cytotoxic cells. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

The aim of the study described in this thesis was to obtain information about the chemical nature of the immunizing antigen of the vaccines against blackleg disease and the mechanism of the immunization. A literature study revealed the existence of much controversy about the reactions caused by Cl. chauvoei germs and toxins. Though the results of serological experiments carried out by various investigators led to the accepted theories about the relationships between homologous lethal toxins and haemolysins~ and between the haemolysis and other reactions of the two different species Cl. chauvoei and Cl. septicum, a comparative chemical study of the toxins had not yet been carried out. A preliminary investigation showed that the soluble immunizing antigen from the Cl. chauvoei cultures had the character of proteins. This was revealed by the loss of activity when pepsin and trypsin were allowed to act upon the antigenic solution and further by the influence of acid and heat upon the antigenic potency. No lethal activity was found in the filtrates of Cl. chauvoei (strain 64) cultures; instead we detected a haemolysin and a hyaluronidase which were also both heat-labile. The isolation procedures for the antigen and haemolysin relied on precipitation with ammonium sulphate and on chromatographic methods. / Thesis (DSc)--University of Pretoria, 1963. / Paraclinical Sciences / DSc / Unrestricted

The genetic relationship between the serologically detectable antigens of the HLA-A and B loci and the mixed lymphocyte culture (MLC) reaction is of utmost importance in the understanding of histocompatibility. From the literature it appeared that neither the HLA-A, B genotype nor the MLC reaction is the complete answer to donorrecipient selection in organ transplantation. This study was therefore initiated in June 1971 in an attempt to clarify the problem. It is inherent in a project of this nature that much time is spent in collecting samples from donors in diverse areas. Most experiments had to be repeated two or three times, therefore some of the problems we set out to resolve were clarified by other workers before we were able to complete our investigations.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.