The cellular immune response to synthetic peptides containing sequences known to be heptenic in performic acid-oxidized ferredoxin from Clostridium pasteurianum

Raising antibodies by coupling peptides to PPD and immunizing BCG-sensitized animals

The use of PPD (purified protein derivative of tuberculin) as a carrier has several significant advantages. It provides very powerful T cell help and it gives rise to virtually no antibody response against itself. This is particularly useful if it is intended to go on to make monoclonal antibodies, where the presence of a large amount of anti-carrier antibody is a nuisance! Furthermore, unlike most comparably powerful adjuvant systems, it can be used in man. PPD coupling has been used to raise antibodies to haptens and to raise T cell responses to tumour cells. It is here reported that small peptides coupled to PPD will give rise to good titres of anti-peptide antibody. For peptides that contain no cysteine, coupling has been achieved by attaching succinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC) to the alpha-amino group of the peptide and N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) to the PPD and allowing an uncleavable bond to form between them. Data on immunization with the leucotactic nonapeptide of the alpha chain of the complement component C3 and with some oncogene-related peptides have been obtained.

The use of unideterminant fragments of ferredoxin in the genetic mapping of determinant specificity of the immune response

The ferredoxin (Fd) molecule is a small non-mammalian immunogenic protein containing 55 amino acid residues with only two major antigenic determinants located with the NH2-terminal heptapeptide and the COOH-terminal pentapeptide. Selective enzyme cleavages of Fd with either trypsin or carboxypeptidase A result in the inactivation of the antigenic determinants by the removal of a tripeptide at the NH2-terminal and two amino acid residues at the COOH-terminal, effectively leaving 52 and 53 amino acid fragments respectively, each containing a single antigenic determinant. Fd digested with both enzymes yielded a 50 amino acid peptide with both determinants inactivated. Purity of these digests was assessed using monoclonal antibodies in standard and antigen-blocking ELISAs. The doubly digested peptide had virtually no reactivity with anti-Fd sera, reconfirming that the central cysteine-rich region is serologically silent. It was found that the sum of the reactivities of the N- and C-determinant-bearing peptides as equal to that of the native Fd and that the ratio of the reactivities could be used to assess determinant selectivity in the response to Fd in congenic recombinant strains of mice. This method was used in mapping the determinant selectivity in the antibody response to the MHC of mice to the left of the I-B subregion. Use of the B10.HTT strain indicated that separate genes mapping to the same subregion code for the magnitude of the antibody response and the determinant selectivity of the response.

The immune response to ferredoxin: characterization of a major idiotype in serum using monoclonal antibody derived by cell fusion

Ferredoxin (Fd) is a low mol. wt protein (6000 d) isolated from Clostridium pasteurianum. This antigen possess two non-cross-reactive antigenic determinants and engenders a restricted antibody response in selected strains of mice. Immunochemical studies of Fd have shown that antibody responses are confined to two sequences of between five and seven amino acids in extent located at the NH2-and COOH-termini of the molecule. Serum antibodies from responder strains of mice bind these epitopes in proportions which are regulated by genes mapping in the Ir-region of the H-2 complex. A hybrid cell line secreting monoclonal Fd-binding antibody has been isolated from an immune mouse through fusion with the SP2/0 myeloma cell line. The resulting antibody binds to a single determinant located at the nH2-terminal of the molecule. An anti-idiotype antibody to this monoclonal antibody was raised in rabbits. After appropriate absorptions, its specificity for the paratopic regions of the hybridoma antibody was established by demonstrating its displacement from reaction with the idiotype by Fd. Analysis of the distribution of the hybridoma idiotype in serum antibodies from congenic mouse strains indicates that it is a major idiotype expressed in different inbred strains sharing identity at the Igh-1 locus.

Localization of antigenic activity and immunogenic capacity in different conformational domains of procollagen peptide

The antibody response to the amino-terminal CNBr peptide of sheep procollagen which consists of a globular and a collagenous segment, was studied in inbred strains of mice. The determinants reacting with antibody could be localized in the globular domain and were lost by reduction of disulfide bridges. The ability to induce an antibody response required the collagen-like sequences and was independent of the triple-helical conformation of this segment. The data were interpreted as indicating a different conformation dependence of hapten and carrier determinants.

The effect of specific cell inactivation on the cellular immune response to ferredoxin peptides

Previous studies using synthetic immunogenic molecules containing two haptenic peptides (ther NH2-terminal heptapeptide and the COOH-terminal pentapeptide of oxidized ferredoxin (O-Fd) from C. pasteurianum) have shown that both peptides individually are capable of initiating lymphocyte transformation and inhibiting migration in populations of lymphocytes from O-Fd-sensitized guinea pigs. While migration inhibition could readily be stimulated by single haptenic peptides, lymphocyte treasformation appeared to be more easily induced by molecules containing two or more haptenic peptides (these could be identical or different) (Kelly, B., Levy, J.G. and Hull, D., Eur. J. Immunol., 1973. 3:574). If lymphocyte transformation is a T cell-mediated phenomenon, these observations indicate the possibility of T cell-T cell interaction. The two haptenic peptides (designated "N" and "C") were synthesized and conjugated to succinylated bovine serum albumin (S-BSA), forming the conjugates N-S-BSA and C-S-BSA, respectively. These conjugates were labeled to high specific activity with 125iodine and were used in an "antigen suicide" procedure to treat guinea pig lymph node cell preparations previously sensitized to O-Fd and keyhole limpet hemocyanin (KLH). Cell populations exposed to either 125I-labeled C-S-BCA demonstrated decreased lymphocyte transformation in the presence of O-Fd but not in the presence of KLH. These results indicate specific cell inactivation by the radioactive peptide conjugates of those cells responsible for initiating cell transformation. Experiments performed by mixing 125I-labeled N-S-BSA-treated cells with 125I-labeled C-S-BSA-treated cells were successful in partially restoring the response to O-Fd and suggest possible synergy between N and C determinant binding cells in the cellular immune response to O-Fd. Evidence from B cell depletion studies suggests that this is a T cell-T cell interaction.