Showing papers by "Richard A. Flavell published in 1990"

Protection of mice against the Lyme disease agent by immunizing with recombinant OspA

Abstract: Lyme borreliosis is a tick-borne illness caused by Borrelia burgdorferi. The gene for outer surface protein A (OspA) from B. burgdorferi strain N40 was cloned into an expression vector and expressed in Escherichia coli. C3H/HeJ mice actively immunized with live transformed E. coli or purified recombinant OspA protein produced antibodies to OspA and were protected from challenge with several strains of B. burgdorferi. Recombinant OspA is a candidate for a vaccine for Lyme borreliosis.

Tolerance in transgenic mice expressing major histocompatibility molecules extrathymically on pancreatic cells.

Abstract: Transgenic mice with defined expression of major histocompatibility complex (MHC) proteins provide novel systems for understanding the fundamental question of T cell tolerance to nonlymphoid self components. The MHC class II I-E and I-A and class I H-2K molecules expressed specifically on pancreatic islet or acinar cells serve as model self antigens. In these systems, transgenic proteins are not detected in the thymus or other lymphoid tissues. Yet mice are tolerant to the pancreatic MHC products in vivo; this tolerance is not induced by clonal deletion. These studies have been aided by monoclonal antibodies specific for I-E-reactive T cells and indicate that clonal anergy may be an important mechanism of tolerance to peripheral proteins.

Infertility in male transgenic mice: disruption of sperm development by HSV-tk expression in postmeiotic germ cells.

Abstract: Previous experiments revealed that male transgenic mice bearing a cosmid that included the Class II E alpha gene, about 35 kb of 5' flanking DNA, and the cosmid vector sequences were sterile. To ascertain the cause of the sterility, various subfragments of the cosmid were tested in transgenic mice. Only those pieces of DNA that included some of the E alpha flanking chromosomal DNA and the herpes simplex virus (HSV)-thymidine kinase (tk) gene that was in the vector resulted in male sterility. Histological analysis revealed abnormalities in nuclear morphology of elongating spermatids and retention of mature spermatids within the seminiferous epithelium. Immunocytochemical studies showed that the HSV-tk gene was expressed at low levels in postmeiotic round spermatids and at higher levels in more mature elongating spermatids. To determine whether expression of HSV-tk in spermatids might be responsible for the sterility, the protamine gene promoter was used to direct the expression of HSV-tk to postmeiotic germ cells. Since the mice so treated were also sterile, the data suggest that expression of this enzyme in spermatids is responsible for the sterility phenotype.

Revised nomenclature of mouse H-2 genes.

Abstract: The H-2 nomenclature was last revised in 1974 (Klein et al. 1974; Shreffler et al. 1974). Since then it has gradually gone out of step with the advances in molecular biology of the H-2 complex as well as the rules for genetic nomenclature established by the International Committee for Mouse Genetic Nomenclature (Lyon 1989). Furthermore, multiple symbols are currently in use designating the same H-2 genes or their products. The present proposal rectifies the existing inconsistencies in the H-2 nomenclature while preserving as much as possible from the previous proposals.

Antigen presentation in MHC class II transgenic mice: stimulation versus tolerization.

Abstract: The immune system must be able to destroy foreign invaders while avoiding damage to self tissues. However, the body contains a complex array of antigens, and the immune system must learn the difference between the universe of self antigens and foreign antigens. In the T-lymphocyte component of tbe immime system, identification of self antigens and induction of tolerance to them takes place mostly within the thymus, through presentation of self antigens to developing T cells. However, self antigens, especially peripheral tissue-specific antigens, cannot all be expressed within the thymus, so \"peripheral tolerance\" requires additional mechanisms. Selective presentation of antigens to the immune system is not likely to be possible, since accessory cells cannot distinguish between self and foreign antigens, and they are exposed to far greater amounts of self antigen relative to foreign antigen. These factors appear to lead to presentation of self antigen to autoreactive T cells, leading to autoimmunity. Yet autoimmune disease is the exception, not the rule. Why? The studies described here entail our recent efforts to understand the mechanisms involved in the generation and maintenance of tolerance to self antigens, with special attention to the issues of peripheral tolerance. Our studies have been greatly aided by the application of transgenic mouse technology, with which we

Clonal Anergy in Transgenic Mice with Pancreatic Expression of MHC Class II I-E

Abstract: Experimental conditions whereby T cell tolerance can be established and maintained have been investigated and defined in many systems. However, the mechanisms of tolerance in these systems and their relevance to tolerance induction during normal T cell development in vivo is still not fully understood. The development of monoclonal antibodies (mAbs) to T cell receptor (TcR) vβ chains, and the observation that certain Vβ chains are associated with reactivity to antigens such as I-E (Kappler, et al. 1987b) and Mls (Kappler, et al. 1988; MacDonald, et al. 1988) has provided in vivo evidence for clonal deletion. Thus, Kappler et al. showed that T cells utilizing the Vβl7a TcR gene which is identified by mAb KJ23 are generally reactive to I-E and are present in I-E negative mice but deleted in the thymus of I-E expressing mouse strains (Kappler, et al. 1987ab, Marrack, et al. 1988). The ability to monitor the presence or absence of antigen-reactive T cells offers a valuable alternative to functional measurements and provides a means to determine mechanisms of T cell tolerance. There is now in vitro evidence for clonal paralysis of T cells. T cell clones are reportedly inactivated upon exposure to antigen in the presence of human T cell clones (Lamb, et al. 1983), chemically modified spleen cells (Jenkins and Schwartz, 1987), purified MHC class II on planar membranes (Quill and Schwartz, 1987), class II+ keratinocytes (Gaspari, et al. 1988), and I-E+ islet cells (Markmann, et al. 1988).