The immune response to oxidized ferredoxin. II. Cross reactivity of cells and antisera to modified ferredoxins and the nature of the cells responding in vitro

The cross reactivity of sera from rabbits sensitized to performic acid oxidized ferredoxin (O-Fd) and of spleen cells from mice sensitized to O-Fd was analysed using several chemically modified forms of ferredoxin in the complement fixation test and the in vitro lymphocyte stimulation assay. Only O-Fd and native ferredoxin (native-Fd) gave positive responses in both assays. Dinitrophenylated-O-Fd (DNP-O-Fd) and acid precipitated ferredoxin (TCA-Fd) were able to fix complement (C') but did not simulate DNA synthesis in vitro. Ferredoxin alkylated with N-ethylmaleimioxin (CM-Fd) was unable to stimulate DNA synthesis and was marginally able to fix C'. Methylated-O-Fd (meth-O-Fd) was not recognized in either assay. The various ferredoxin preparations were tested for their ability to sensitize mice for use in the in vitro lymphocyte stimulation assay. Only O-Fd, NEM-Fd and native-Fd were capable of sensitizing lymphocytes for a proliferative response in vitro to the test antigens. This correlates with the observation that only these antigens were able to induce DNA synthesis in O-Fd-sensitized lymphocytes. The nature of the cells responding in vitro was examined by treating the cells with rabbit anti-mouse immunoglobulin and C' or rabbit anti-mouse brain associated theta and C'. The 24-hr response was found to be sensitive to both sera while the 120-hr response was sensitive only to the anti-theta sera.

The immune response to oxidized ferredoxin. I. Specificity of the response to the amino terminal determinant

Several synthetic peptide analogues of the amino terminal antigenic determinant (ala-tyr-lysile-ala-asp-ser) of oxidized ferredoxin (O-Fd) were tested for their ability to inhibit the complement fixation reaction between O-Fd and homologous rabbit antiserum, and to inhibit the migration of spleen cells from guinea-pigs immunized to O-Fd or to a conjugate of the amino terminal heptapeptide (N7) and bovine serum albumin (N7-BSA). The results of the migration inhibition assay suggest that the tetrapeptide and longer peptides of the native sequence were all recognized and stimulated the production of migration inhibition factor. Peptides modified at the aspartic residue were partially active while the serine modified peptide was not. Modification at the amino end of the heptapeptide had no effect on migration inhibition. As specificity controls, it was shown that the N7-BSA conjugate inhibited migration in O-Fd immunized animals, while O-Fd inhibited migration in N7-BSA immunized animals. The hexa-, hepta-, aspartic-deleted and serine-modified peptides were able to inhibit the complement fixation reaction with O-Fd and specific rabbit antiserum. Inhibition found with the serine-modified peptide and the lack of inhibition with the amino-modified peptide or the di-, tri-, tetra- and pentapeptides indicates the determinant recognized by the rabbit antibodies is either larger or is located nearer the middle of the heptapeptide than the determinant which induced the production of MIF.

Responses of guinea-pig lymphocytes to mitogens, an antigen, and mixed leucocyte culture in media with and without mercaptoethanol and foetal calf serum

The ability of guinea-pig spleen and lymph node cells to undergo a proliferative response in vitro in the presence of mitogens (concanavalin A and lipopolysaccharide), a specific antigen (oxidized ferredoxin), and allogeneic cells was assessed under a variety of conditions. Time and dose dependency of the responses was measured in RPMI 1640, RPMI 1640 plus mercaptoethanol (ME), RPMI 1640 plus foetal calf serum (FCS), and RPMI 1640 with ME and FCS. Mitogen responses were also measured after treatment of the cells with sheep antiguinea pig immunoglobulin (SaGPIg) and complement (C') or after passage through nylon wool columns. Lipopolysaccharide (LPS) stimulated the cells under all media conditions over a wide range of concentrations but over a narrow time period. Nylon wool treatment of the cells eliminated the LPS response while SaGPIg and C' reduced it. Concanavalin A (con A) stimulated the cells under all test conditions and demonstrated a dose-time interrelationship in terms of maximum response. Pre-treatment of cells with SaGPIg and C' enhanced the response to con A while nylon wool fractionation diminished it somewhat. Only lymph node cells responded in vitro to oxidized ferredoxin (OFd). In serum-free media the OFd responses were maximal at 48 hours whereas in media containing FCS proliferative responses were supported for a prolonged period and appeared to be bimodal. Except for an early response with RPMI 1640 and ME, only media containing FCS supported stimulation in the mixed leucocyte culture.

Cellular co-operation by mouse lymphocytes to chemically defined antigens

When populations of mouse spleen cells were treated with a highly radioactive 125I-labelled haptenic conjugate (125I-labelled PDG-N) and subsequently injected into X-irradiated, immunized (N-10-C) syngeneic BALB/c mice, it was found that after autoradiography with 125I-labelled N and C haptenic conjugates, the numbers of ABC to both the N and C haptens decreased. The number of ABC found were significantly lower than those found in mice that had been reconstituted with cells "suicided" with another 125I-labelled antigen (125I-labelled BSA) and subsequently immunized with N-10-C.

Studies with a gluconate-6-phosphate dehydrogenase mutant in Escherichia coli strain C

A map location of the gluconate-6-phosphate dehydrogenase (gnd) marker was estimated in Escherichia coli C at approximately 46 min by P1 transduction. The gnd locus appears to lie between the co-transducible histidine and prophage P2 location I markers.