Localization of the prostaglandin F2 alpha receptor in rat tissues.

The localization of the prostaglandin F2alpha (FP) receptor was examined in rat tissues by immunohistochemistry and in situ hybridization. Immunohistochemistry on paraffin sections was performed with a rabbit polyclonal antiserum raised against a synthetic peptide derived from the rat FP receptor sequence. In situ hybridization on cryosections was done with 35S-labelled rat FP receptor antisense and sense riboprobes. The most intense FP receptor-like immunoreactivity was observed in granulosa luteal cells, muscle and epithelial cells, e.g. cardiac, skeletal and smooth muscle, and hepatocytes. Weaker immunoreactivity was found in connective tissue fibroblasts. In the eye, intense immunostaining was associated with the corneal and conjunctival epithelium and moderate staining with the ciliary body, retina, iris and connective tissues. In situ hybridization generally confirmed the results. The riboprobe hybridized weakly with the heart, skeletal muscle, uterus, liver, lung and corpus luteum. Thus, the prostaglandin FP receptor was found to be widely distributed in rat tissues.

T and B cell responses to chimeric proteins containing heterologous T helper epitopes inserted at different positions.

The ability of a T helper (Th) epitope to induce help for B cells recognizing different determinants within a multideterminant antigen was investigated. Chimeric fusion proteins, containing inserts of single or multiple copies of the Th epitope ovalbumin 323-339 (ova) at two different positions, were compared with respect to their ability to induce specific antibody production and ova-specific T cell activation. The antibody responses against B cell determinants at the amino and carboxy terminus, respectively was differently influenced by the molecular positioning of the inserted Th determinant. All ova-containing fusion proteins induced antibody production against the B cell determinant at the amino terminal end irrespective of the positioning of ova. In addition, multiple copies of ova in any position led to increased levels of antibody production against this epitope. In contrast, T cell help for antibody production against the determinant at the carboxy terminus was more effective after insertion of multiple copies of ova in a distal than in an adjacent position. Furthermore a fusion protein, containing four copies of ova effectively elicited T cell help for high levels of antibody production against both examined B cell determinants, showing that activated Th cells recognizing a single epitope could simultaneously provide help for distinct sets of B cells specific for widely separated epitopes within a protein. Immunodominant T cell recognition of ova in all chimeric peptides, independently of its position, was demonstrated by lymph node cell (LNC) proliferation of primed BALB/c mice. The level of ova-specific T cell proliferation was similar, irrespective of which chimeric peptide that had been used for priming, and thus did not reveal any differences in T cell priming efficiencies related to the number of ova copies in the fusion proteins. However, when the peptides were presented to a ova-specific T cell line by A20 B lymphoma cells, a close correlation between IL-2 production by the clonal T cells and the number of ova epitopes in the chimeric peptides was observed. Thus, increased cytokine production by ova-specific T cells may be important for the increased level of in vivo antibody production observed in response to multiple copies of ova in the chimeric antigens.

Enhanced immunogenicity of recombinant peptide fusions containing multiple copies of a heterologous T helper epitope.

We have examined the immune response against the nonimmunogenic heat-stable enterotoxin (STa) of enterotoxigenic Escherichia coli using recombinant fusion proteins containing the STa-peptide linked to an IgG-binding analogue of protein A and varying numbers of the T helper epitope 323-339 from ovalbumin (ova). By immunization of inbred strains of mice with a series of STa fusion proteins, containing up to four copies of ova tandemly multiplied, we demonstrated that the anti-STa antibody response is controlled by ova-specific T helper cells in a genetically restricted manner. In the responding mouse strains (2 out of 3 tested), the level of antibody production was increased by addition of multiple ova epitopes, the anti-STa response being considerably higher to fusion proteins containing four than one or two ova epitopes.

Anticardiolipin antibodies in patients with systemic lupus erythematosus.

We studied a group of 59 unselected patients with systemic lupus erythematosus (SLE); these patients were from a defined population who lived in southern Sweden. We found that serum concentrations of anticardiolipin antibodies were increased in 32 SLE patients (54.2%). No significant correlation between increased amounts of anticardiolipin antibodies and clinical symptoms, such as thrombocytopenia or thrombosis, was found. Serial serum samples from 28 patients (12 patients were from the epidemiologic cohort) were analyzed. Sixteen of these 28 patients (57.1%) had increased levels of anticardiolipin antibodies; in most cases, there was no variation in these values with regard to clinical disease flares or treatment. Increased concentrations of anticardiolipin were observed in 4 patients with cerebral infarction. However, very high concentrations of anticardiolipin antibodies were observed in several patients with inactive SLE who had no history of thrombosis or thrombocytopenia. Our results underscore the importance of studying unselected patient groups when correlating laboratory data with clinical manifestations of disease.