CD38 is a 42-kilodalton glycoprotein expressed extensively on B and T lymphocytes. CD38 exhibits a structural homology to Aplysia adenosine diphosphate (ADP)-ribosyl cyclase. This enzyme catalyzes the synthesis of cyclic ADP-ribose (cADPR), a metabolite of nicotinamide adenine dinucleotide (NAD+) with calcium-mobilizing activity. A complementary DNA encoding the extracellular domain of murine CD38 was constructed and expressed, and the resultant recombinant soluble CD38 was purified to homogeneity. Soluble CD38 catalyzed the formation and hydrolysis of cADPR when added to NAD+. Purified cADPR augmented the proliferative response of activated murine B cells, potentially implicating the enzymatic activity of CD38 in lymphocyte function.

A mouse monoclonal antibody (MoAb), reactive with a repetitive carbohydrate epitope on lentil-lectin adherent glycoproteins present on the surface and in the secretions of Taenia saginata cysticerci, was used in the construction of a diagnostic ELISA assay to detect these glycoproteins in the serum of T. saginata infected cattle. The MoAb was used as the trapping layer and subsequently bound glycoprotein was revealed using the same MoAb and biotinylated peroxidase-streptavidin complex as the developing system. The assay was suitably specific. Exceptionally low background values were obtained with sera from animals with a range of commonly occurring tropical parasitic infections, including Taenia hydatigena, Echinococcus granulosus and Fasciola gigantica. The minimal detection level was approximately 200 live cysticerci in cattle. Parasite derived glycoprotein could be detected in serum from about 4-5 weeks post-infection onwards and was associated with a current infection, as drug treatment of infected cattle to kill the cysticerci resulted in the disappearance of these components from the circulation, while the titre of anti-parasite antibody remained high. The same assay also detected Taenia solium cysticercosis in humans.

The efficacy of albendazole (ABZ) treatment for human neurocysticercosis (NCC) was assessed by using a monoclonal antibody-based parasite antigen detection ELISA which specifically detects the products of living cysticerci in human serum. The assay displayed 85% diagnostic sensitivity, detecting 39 of 46 NCC cases. Only patients with a single viable cyst or only enhancing lesions (degenerating parasites) were seronegative. Specificity of the assay was 92% (23/25) when tested in healthy Peruvian volunteers. In 'cured' patients, in whom all parasites died after ABZ therapy, parasite antigen levels fell sharply by 3 months post treatment. This pattern was not observed in patients refractory to treatment. The sensitivity of the assay with serum samples, and its ability to identify successfully treated patients, make this monoclonal antibody-based ELISA the test of choice for the follow-up of NCC cases.

The aim of this study was to investigate the importance of cellular immunity in foot-and-mouth disease in cattle, in particular to determine whether a CD8 M T-cell response could be detected, as these cells may play a role in both immunity and virus persistence. As attempts to characterize classical cytotoxic T cells had yielded non-reproducible results, largely due to high backgrounds in control cultures, a proliferation assay was developed that was demonstrated to detect antigenspecific, MHC class I-restricted bovine CD8 M cells responding to foot-and-mouth disease virus (FMDV). Proliferative CD8 M T-cell responses were detected consistently from 10 to 14 days following infection with FMDV and typically lasted 3-4 weeks. The role of CD8 M T cells in control of the disease, in particular their relevance for the establishment of persistence, may now be investigated.

(3,4). These 1gM polymers also consisted of mixtures of hexamers and pentamers. Davis et al. (3) demonstrated that the hexameric form of the IgM molecule was functional. They found that hexameric IgM activated the complement cascade in hemolytic assays up to 20-fold more efficiently than pentameric IgM, an observation confirmed and extended in our own studies (9). We found that inducible B-cell lines could secrete IgM hexamers, but the relative levels of hexameric to pentameric IgM varied depending on the cell line, thus leading to differences in the activity of the secreted IgM. Taken together, these studies show that J chain is not required for either assembly or secretion of IgM. It is unclear, however, if the production of hexamers is an intrinsic property of particular cell lines, such that they cannot polymerize IgM "correctly," or if the ratio of IgM hexamers and pentamers reflects a limited abundance or inaccessibility of J chain to the polymerizing IgM. When J chain is absent or in limited supply, a sixth IgM monomer might be inserted into the assembling polymer in place of J chain.In the current study, we have tested this hypothesis. From earlier work using the inducible B-cell lymphoma CH12, we had found that synthesis of J chain RNA could be stimulated to a greater extent by lymphokine-containing supernatants than by lipopolysaccharide (LPS) (11). Here we demonstrate that while both LPS and interleukin (IL)-5 stimulate the differentiation of CH12 cells, IL-5 stimulates the production ofJ chain protein to a higher level than LPS. This differential stimulation correlates with the production of fewer IgM hexamers in the IL-5-stimulated population, thus lowering the biological activity of the secreted IgM, as measured by activation of the complement cascade. The functional significance of this result for our understanding of the regulation of the primary immune response is discussed. MATERIALS AND METHODS

Eight neutralizing and two non-neutralizing antifoot-and-mouth disease virus (FMDV) bovine IgG1 and IgG2 monoclonal antibodies (BMAbs) recognize conformationally dependent epitopes. The majority of those shown to neutralize virus passively protected mice from virus challenge, regardless of isotype. Well-characterized anti-FMDV mouse MAbs, representing five independent neutralizing epitopes on O 1 serotype virus, were examined with each of the ten BMAbs in a competition-based ELISA. Five of the neutralizing BMAbs (C48, C65, C74, C83 and MH6) were shown to be directed against epitopes on, or in close proximity to, that previously defined as neutralizing antigenic site 2. Another neutralizing BMAb, MH5, bound to an epitope on, or in close proximity to antigenic site 3. Two neutralizing BMAbs (C2 and C96) simultaneously

SUMMARYThe CD3-T-cell receptor complex is the clonotypic surface structure by which T lymphocytes recognize foreign antigens and are subsequently activated. Because of the low immunogenicity of the CD3 molecules, anti-CD3 monoclonal antibodies (mAb) are difficult to prepare and have not been available in several species. Following isolation of porcine CD3, 14 anti-porcine CD3 mAb were prepared, which define six groups of CD3-e epitopes, coprecipitate two types of TCR and reveal considerable heterogeneity of CD3 expression amongst lymphocyte subpopulations. Thus, both CD3 positive and negative subpopulations of CD2 or CD8 positive cells were found in the blood. The density of CD3 on CD2 or CD8 cells was relatively low and heterogeneous, whereas the CD2 ÿ , CD8 ÿ or MAC320 T cells expressed CD3 at a higher and more homogeneous level. Finally, in the thymus, staining with anti-CD3 resolved large thymocytes into two subsets: one expressing a high level of CD3 and the other being negative. In contrast, small thymocytes expressed CD3 at a low and more homogeneous level. Immunohistological studies confirmed the presence of clearly detectable CD3 in thymus medulla and the T-cell regions of peripheral lymphoid tissues. Most of the mAb were mitogenic, when presented to peripheral blood mononuclear cells in immobilized form. The anti-CD3 mAb also induced redirected cytotoxicity which was shown to be Fc receptor dependent.

Eosinophils have long been thought to be effectors of immunity to helminths but have also been implicated in the pathogenesis of asthma. Patterns of cytokine production in the host