The ability of Leiophron uniformis (Gahan) to parasitize 4 Lygus spp. was determined. While L. uniformis readily attacked Lygus hesperus (Knight), L. lineolaris (Palisot de Beauvois), L. elisus Van Duzee, and L. desertinus Knight, only 6.7% of the L. lineolaris attacked were parasitized compared to 84-87% parasitization of the other species. Two factors were found to cause the low rate of parasitism of L. lineolaris. L. uniformis oviposited in (accepted) few of the L. lineolaris nymphs attacked and most eggs found were encapsulated by the host. Nymphs less than 48-hr old were readily parasitized because they were accepted by the wasps and the hosts encapsulated few of the parasitoid eggs. As nymphal age increased, parasitism dropped rapidly as the acceptance of the host decreased and the host's encapsulation ability increased. Different strains of L. lineolaris were found to differ greatly in their susceptibility to parasitism, their ability to encapsulate, and their acceptance by the parasitoids. A host strain from Arizona was very resistant to parasitism, whereas a strain from Delaware (NJLBR) that had been in culture for 7 years was easily parasitized. The NJLBR strain had no encapsulating ability and it was readily accepted by L. uniformis. A recently established host strain from Delaware (DELBR) encapsulated 23-27% of the parasitoid eggs while an Arizona strain (FILBR) encapsulated 66-76% of the eggs. The DELBR nymphs were accepted in 42-43% of the attacks while the FILBR nymphs were accepted in only 5-14% of the attacks. Delaware and California parasitoid strains did not differ in their acceptance of L. lineolaris or in their ability to resist encapsulation. Rearing L. uniformis for only 1 generation on L. lineolaris did not precondition the wasps to accept that species as a host in preference to L. hesperus. L. uniformis, which had been reared on L. lineolaris for 5 or more generations, did accept that host 2.5 times as often as wasps reared on L. hesperus. The parasitoids did not known any increase in resistance to encapsulation even after they had been reared on L. lineolaris for 11 generations.

No description available.

No description available.

No description available.

Host Defense Peptides (HDPs) are small, cationic and amphipathic molecules with inherent antimicrobial and immunomodular function. However their effects on blood-derived T cells is unknown and is the focus of this investigation. In this thesis, porcine peripheral blood mononuclear cells (PBMCs) were stimulated with bovine myeloid antimicrobial peptide (BMAP)-27, BMAP-28, Indolicidin (Indol), or HH2 in the presence and absence of Concanavalin A (ConA). It was observed that BMAP-27, BMAP-28, and Indol inhibited ConA-stimulated porcine PBMC proliferation. To ensure that the observed effect on cell proliferation was not simply due to a physical interaction between the peptide and ConA, addition of peptide and ConA was staggered. Porcine CD4+/CD8+ T cells were isolated from blood using magnetic activating cell sorting (MACS) and it was determined that BMAP-27 and BMAP-28 inhibited ConA-stimulated T cell proliferation. They did not promote T cell necrosis, but approximately 40 % of the activated T cells undergoes apoptosis in the presence of BMAP-27 and BMAP-28. The remaining 60 % of the T cells consumed very little ATP and showed an increase in expression of cytotoxic T lymphocyte antigen-4 (CTLA-4), indicating the induction of T cell anergy. The addition of exogenous IL-2 decreased the surface expression of CTLA-4 in ConA- activated CD4+ T cells and induced renewed CD4+/CD8+ T cell proliferation, an indicator that these cells underwent activation-induced anergy. Thus, we submit that BMAP-27 and BMAP-28 may play a role in returning the activated T cell population to a homeostatic state through induction of peripheral tolerance mechanisms.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

Thesis (Ph.D.)--University of Adelaide, Dept. of Applied & Molecular Ecology, 2002. / Bibliography: leaves 113-144.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 109-129).