Search

Freshly isolated allogenic pancreatic islets transplanted into the thymus of transiently immunosuppressed rats are not rejected but survive indefinitely while also inducing a state of specific unresponsiveness that permits survival of secondary donor-strain islets transplanted extrathymically. Since freshly isolated pancreatic islets contain intraislet antigen-presenting cells as well as endocrine cells it is unclear which cellular component is primarily responsible for mediating unresponsiveness. We therefore examined the impact of pretransplant in vitro culture (a maneuver which selectively depletes intraislet APCs) on the capacity of islet allografts to induce unresponsiveness after intrathymic implantation. APC-depleted pancreatic islets, which are known to have reduced immunogenicity, survived indefinitely in the thymus of allogeneic hosts whether or not brief immunosuppression was employed, but failed to promote survival of subsequent donor-strain islets transplanted to an extrathymic site. These findings emphasize the central role of APCs in the induction of transplantation tolerance in this model, and are consistent with the established role of this population in the development of T cell tolerance in the thymus.

The use of cocaine in the United States has reached near epidemic proportions. A major factor responsible for the dramatic increase in cocaine use is the ability to freebase cocaine and extract essentially pure drug to be smoked as crack. As a result, a variety of respiratory problems temporally associated with crack inhalation have been reported. Cocaine may cause changes in the respiratory tract as a result of its pharmacologic effects exerted either locally or systemically, its method of administration (smoking, sniffing, injecting), or its alteration of central nervous system neuroregulation of pulmonary function. These changes include such diverse disorders as thermal airway injury, pulmonary edema and hemorrhage, hypersensitivity reactions, and interstitial lung disease. However, a review of the pulmonary pathology and dysfunction associated with crack and/or cocaine use indicates that the reported changes are most likely multifactorial, even idiosyncratic, and fails to reveal common features diagnostic of cocaine use. It is likely that the spectrum of cocaine-induced pulmonary disease will continue to enlarge.