Cellular immune response of lymph nodes from dogs following the intradermal injection of a recombinant antigen corresponding to a 66 kDa protein of Echinococcus granulosus.

A recombinant polypeptide (referred to as EgA31), which represents a 66kDa protein, was prepared from an Echinococcus granulosus cDNA library. In order to assess its potential to induce cellular immune responses, dog popliteal and prescapular lymph nodes were sensitized with this recombinant polypeptide. Subpopulations of lymphocytes were then analyzed by flow cytometry and immunohistochemistry on lymph node sections. Five days after the sensitization, the paracortical areas of the lymph nodes appeared hypertrophic, the number of CD3+, CD4+, CD8+ and CD5+ cells increased, the number of B-cells began to augment and some secondary follicles occurred, and a number of CD4+ cells appeared in germinal centers. Many large secondary follicles and a significantly augmented number of CD5+ cells in cords of medullae were observed 10 days after the sensitization. These active cellular responses strengthen the interest for further studies on the development of a vaccine with this recombinant polypeptide.

Immunophenotypic characterization of feline Langerhans cells.

To carry out the characterization of feline Langerhans cells (LC), first described in 1994, we used a panel of monoclonal antibodies (MAb) known to react with human, canine and feline leukocyte membrane antigens (Ag). The immunolabeling was performed, at light microscope level, on frozen sections of feline skin and labial mucosa using an avidin-biotin-peroxidase technique, and at electron microscope level on epidermal cell suspensions using an immunogold technique. Out of the 52 MAb tested, six labeled basal or suprabasal DC cells in the frozen sections, either in epidermis or lip epithelium: MHM23 (anti-human CD18), CVS20 and vpg3 (respectively anti-canine and feline-major histocompatibility complex class II molecules), vpg5 (anti-feline leukocytes), vpg39 (anti-feline CD4) and Fel5F4 (anti-feline CD1a). These six MAb were used on suspensions, and labeled cells which showed no desmosomes or melanosomes, but contained 'zipper-like' structures similar to Birbeck granules (BG) in their cytoplasm, revealing they were LC. Consequently, feline LC are CD18-positive (CD18+), major histocompatibility complex class II-positive (Class II+), CD1a-positive (CD1a+), vpg5-positive (vg5+) and CD4-positive (CD4+). This immunophenotypic and ultrastructural characterization demonstrates that feline LC share many characteristics with their human counterparts, a fact that will allow us to study the role of feline LC in certain feline diseases such as Feline Immunodeficiency Virus (FIV) infection, since it has been shown that human LC cells are HIV-permissive, and to establish an animal model for human AIDS.

Quantitative assessment of feline epidermal Langerhans cells.

The densities of feline epidermal dendritic cells expressing CD18, MHC class II and CD1a antigens were determined for four anatomical locations in 19 cats of European breed in blind conditions. The densities (+/- SD) of CD1a+ Langerhans cells in the skin of the abdominal wall (269 +/- 68 cells/mm2), the back (363 +/- 19), the internal side of the ear (572 +/- 30) and the external side of the ear (502 +/- 32) were significantly different, with young and old animals displaying less stained cells than adults. No significant differences in the mean densities were found with regard to sex, colour or antibody used.