Passive transfer of resistance in rabbits infested with adultIxodes ricinus L.: Humoral factors influence feeding and egg laying

Summary Partial immunity against the bites of I. ricinus was transferred to normal rabbits by inoculating immune serum from resistant animals. Transferred humoral factors diminished the weight f the ticks' blood meal by 29% and increased the feeding period by about 1 day in comparison with ectoparasites engorged on controls. They provoked also the failure of egg laying by I. ricinus. Only 55% of ticks fed on treated rabbits laid eggs (94% on controls). The immunological state of immune serum donors or recipients was studied and the IgG and homocytotropic specific anti-I. ricinus antibodies were identified. The immediate hypersensitivity of rabbits' skin was also controlled.The present work was supported by the Swiss National Fund for Scientific Research, grant No. 3.558.75.     

Effects and duration of resistance acquired by rabbits on feeding and egg laying in Ixodes ricinus L.

Rabbits gradually developed a resistance against Ixodes ricinus ticks as a result of sequential experimental infestations. The resistance was characterized by an increase duration of feeding, by ticks engorging to a smaller extent and by reduced egg production. Once established, the immunity persisted for at least 9 months. Changes in the titre of circulating anti-I. ricinus antibodies was measured by indirect immunofluorescence.     

Effects and duration of resistance acquired by rabbits on feeding and egg laying in Ixodes ricinus L.

Summary Rabbits gradually developed a resistance against Ixodes ricinus ticks as a result of sequential experimental infestations. The resistance was characterized by an increased duration of feeding, by ticks engorging to a smaller extent and by reduced egg production. Once established, the immunity persisted for at least 9 months. Changes in the titre of circulating anti-I. ricinus antibodies was measured by indirect immunofluorescence.The present work was supported by the Swiss National Fund for Scientific Research, grant No. 3.558-0.75.     

Rabbits infested with adultIxodes ricinus L.: Effects of mepyramine on acquired resistance

Summary The results of this work demonstrate that histamine seems to be involved in the expression of the resistance acquired by rabbits to I. ricunus. Daily treatment of animals with the H₁-antihistaminic mepyramine inhibited the effects of immunity. This observation applies to the effect of resistance on the weight of engorged ticks, the duration of the blood meal and the success of egg laying and hatching.The present work was supported by the Swiss National Fund for Research, grant No. 3.303-78. We are grateful to Dr L. Julou (Rhône-Poulenc) for a gift of mepyramine.     

Passage of hemolysins through the midgut epithelium of femaleIxodes ricinus L. fed on rabbits infested or reinfested with ticks

Summary Antibodies considered in this study are hemolysins synthesized by rabbits against sheep red blood cells. Ingested with the blood meal, they cross the tick midgut epithelium and retain their immunological properties in the hemolymph. During a reinfestation of rabbits, more ticks present these antibodies, and titres are generally higher than during a first infestation. Hemolysins are only found in ticks weighing 180 mg or more.The present work was supported by the Swiss National Foundation for Scientific Research, grant No. 3070.81.     

Common antigenic properties of a g-type (goose) and a c-type (duck) egg white lysozyme: Antibody responses in rabbits and mice

Embden goose (GEWL) and Barbary duck (DEWL) egg white lysozymes possess different amino acid sequences corresponding to the g-type and c-type, respectively. GEWL was shown to be a better immunogen than DEWL in both rabbits and mice. The antigenicity of the two lysozymes was tested using different technique (i.e. indirect ELISA, inhibition tests and immunoabsorption experiments). Injection of either GEWL or DEWL into rabbits and mice induced both specific antibodies and cross-reacting antibodies. Moreover, anti-GEWL antibodies, in contrast to anti-DEWL antibodies, did not cross-react with hen egg white lysozyme (HEWL), a c-type lysozyme. While the structure of GEWL was not modified after binding to plastic, DEWL was denaturated, but it did keep some native epitopes. It was concluded that g-type and c-type lysozymes, which have different amino acid sequences, exhibit strong common antigenic properties.     

Subpopulations of T-lymphocytes in Peyer's patches: sensitivity to antilymphocyte serum and adult thymectomy.

Anti-lymphocyte (ALS) treatment or adult thymectomy of the donor have been shown to depress respectively the cell proliferation and the cytotoxicity in the graft-versus-host (GVH) reaction. A quantitative assay and the histological criteria of the GVH reaction have been used to demonstrate that all the known subpopulations of T-lymphocytes involved in the GVH reaction are present in the Peyer's patches as well as in the spleen and mesenteric lymph nodes in the rat.     

The stimulus transmitting apparatus in the trichobothria of the bugsPyrrhocoris apterus L. andDysdercus intermedius (Dist.) and its influence on the dynamic of excitation in these sensilla

Correlations exist between ultrastructural characteristics in the stimulus-transmitting apparatus of the trichobothria on the 4th abdominal segment of the bugPyrrhocoris apterus (L.) and the functional characteristics of these sensilla.     

Studies on experimental ancylostomiasis: transfer of acquired immunity to Ancylostoma caninum in mice through sensitized thymus and bone marrow cells.

An attempt has been made to transfer acquired immunity to Ancylostoma caninum infective larvae from infected Swiss albino female mice to nonimmune, isologous recipients of same sex, through immunized thymus and bone marrow cells. Immunized cells from donors infected with a single high dose of 1000 larvae were found to be more immunocompetent than cells from donors infected with a single, but low dose of 500 larvae.