Apidaecins: antibacterial peptides from honeybees.

Although insects lack the basic entities of the vertebrate immune system, such as lymphocytes and immunoglobulins, they have developed alternative defence mechanisms against infections. Different types of peptide factors, exhibiting bactericidal activity, have been detected in some insect species. These humoral factors are induced upon infection.

Conserved epitopes on plant H1 histones recognized by monoclonal antibodies.

A series of monoclonal antibodies specific for distinct regions of H1 histone from the plant Nicotiana tabacum were obtained from fusion experiments with spleen cells of mice immunized with tobacco nuclear extracts. These monoclonal antibodies were characterized and the evolutionary conservation of the epitopes in higher plants and animals studied by immunoblotting and enzyme-linked immunosorbent assay (ELISA). Whereas some epitopes appear restricted to the Solanaceae plant family, others are common to all higher eukaryotes tested and even detectable on nuclear proteins of yeast.

Monoclonal Antibody Analysis and Insecticidal Spectrum of Three Types of Lepidopteran-Specific Insecticidal Crystal Proteins of Bacillus thuringiensis.

We have investigated the protein composition and the insecticidal spectrum of crystals of 29 Bacillus thuringiensis strains active against lepidopteran larvae. All crystals contained proteins of 130 to 140 kilodaltons (kDa) which could be grouped into three types by the molecular weight of the protoxin and the trypsin-activated core fragment. Proteins of the three types showed a characteristic insecticidal spectrum when tested against five lepidopteran species.

Common features of Bacillus thuringiensis toxins specific for Diptera and Lepidoptera.

The complete nucleotide sequence of a cloned gene encoding a 130-kDa crystal protein of Bacillus thuringiensis (B.t.) subspecies israelensis has been determined.

T-cell mediated immunity in murine malaria. I. Induction of T-cell dependent proliferative responses to Plasmodium chabaudi.

To investigate the mechanisms of cell mediated immunity to malaria, we studied different systems to measure specific activation of T lymphocytes by P. chabaudi antigens. Mice were primed by subcutaneous administration of parasite antigens followed by co-cultivation of lymphocytes taken from the draining lymph nodes in the presence of the priming antigen.

Rabbit leukocyte surface antigens defined by monoclonal antibodies.

Several monoclonal antibodies (mAb) against rabbit leukocytes were characterized in binding and functional studies. mAb 1.24 stains thymocytes, bone marrow cells, peripheral T and B cells and blood monocytes.

The immunomodulatory effect of anti-Micrococcus luteus antibodies. I. Effect on in vitro rabbit T cell functions.

A range of purified rabbit anti-Micrococcus luteus antibodies (anti-MCAb) were tested for their ability to interfere with a variety of in vitro immune responses. Such antibodies strongly inhibited the secondary IgG antibody response to sheep red blood cells without affecting the IgM response or the proliferative responses to mitogens and antigens. By exposing lymphocyte populations to anti-MCAb, it was found that such reagents exerted a strong mitogenic effect on rabbit T lymphocytes, provided these cells were derived from antigen-activated lymph nodes.

Modulation of the immune response by antibacterial antibodies.

Antibodies induced by the gram+ bacteria Micrococcus lysodeikticus exhibit different carbohydrate specificities and hence might cross-react with membrane glycoproteins and/or glycolipids of mammalian cells. Using a T cell derived lymphoid line, these antibodies were found to detect a membrane marker which is only exposed in confluent culture conditions on non-dividing cells. Such confluence related antigen (Cag) is a cryptic membrane antigen, which can be unmasked through membrane perturbating agents such as p-formaldehyde or through interactions with macrophages and macrophage derived factors.

Effects of anti-Ig reagents on T cell functions I. Activation of rabbit T cells by anti-allotype antibodies.

Rabbit lymphocytes were analyzed by flow microfluorometry, using anti-T cell and anti-Ig reagents. Rabbit T cells and cells expressing surface Ig (B cells) appeared to belong to distinct subpopulations which could be separated on the basis of their selective adherence to nylon wool columns or to anti-Ig-coated dishes. Using flow microfluorometry, no evidence was obtained for the expression of a allotypes (VH framework) on T cells.

Production of IgG-specific auto-anti-allotypes in b4.2-suppressed rabbits.

Rabbits were completely suppressed for kappa chain allotype b4.2, and autoantibodies against b4.1 or b4.

Antigen-induced proliferation assay for rabbit T lymphocytes. I. Characteristics of the response.

An in vitro assay which measures specific antigen-induced proliferation of primed rabbit lymph node and peripheral blood cells is described. This response was found to be mediated by T cells, since it could be obtained with nylon-wool passed cells and cells which do not adhere to anti-Ig-coated plastic plates. The proliferative response was found to be highly antigen-specific and restricted to the draining lymph node if assessed up to 15 days post-priming.

Histamine-binding suppressor T cells in rabbit peripheral blood.

Peripheral blood leukocytes (PBL) from primed rabbits were able to suppress the in vitro anti-sheep red blood cell (SRBC) plaque-forming cell (PFC) response of autologous spleen cells. A population containing the suppressor cells could be isolated from PBL by cell fractionation on columns of insolubilized histamine. In contrast to spleen cells, PBL generatd a weak secondary anti-SRBC response in vitro.