Properties of rat tracheal epithelial cells separated based on expression of cell surface alpha-galactosyl end groups.

We used Griffonia (bandeiraea) simplicifolia I (GS I) lectin and flow cytometry to isolate subsets of rat tracheal epithelial cells based on the presence or absence of cell surface alpha-galactosyl end groups. These fractions were designated GS I-positive and -negative, respectively. Ninety-eight percent of the cells in the GS I-positive fraction expressed cell surface alpha-galactosyl end groups; 95% had immunocytochemically detectable keratin 14-related protein (a basal cell marker) and 98% lacked alcian blue-periodic acid-Schiff (AB-PAS)-stained cytoplasmic granules. More than 90% of the GS I-positive cells had a high nuclear-to-cytoplasm ratio, had tonofilaments, and lacked organelles characteristic of other differentiated cell types; they were thus classified as basal cells. In bioassays, the GS I-positive fraction had a colony-forming efficiency greater than or equal to that of native tracheal cell suspensions, and the cells were able to repopulate denuded tracheal grafts with ciliated, secretory, and basal cells. More than 99% of the cells in the GS I-negative fraction lacked cell surface alpha-galactosyl end groups, 98% did not stain for keratin 14-related protein, 54% had significant numbers of AB-PAS-stained cytoplasmic granules, and 16% were identified as ciliated cells. The GS I-negative fraction had a lower colony-forming efficiency than the GS I-positive fraction but, it too, was able to repopulate denuded tracheal grafts with a complete mucociliary epithelium. These results show that both GS I-positive and -negative cells had the potential to proliferate and differentiate into the major tracheal cell types

Pentamidine: An inhibitor of interleukin-1 that acts via a post-translational event

Pharmacologic inhibition of cytokines, particularly interleukin-1 (IL-1), potentially has numerous therapeutic applications in inflammatory diseases. We demonstrate that pentamidine, an aromatic diamidine currently used to treat Pneumocystis carinii pneumonia, is a specific and effective inhibitor of cellular IL-1 release from macrophages, and we have shown that this blockage occurs at neither the transcriptional nor the translational level. Pentamidine induced inhibition of IL-1 occurs via an alteration in the post-translational modification of the protein, altering the intracellular and/or membrane cleavage of the 31-kDa pro-IL-1 to the 17-kDa secreted form. In addition, pentamidine exhibited less broad immunosuppressive actions when compared to a corticosteroid, the classical therapeutics utilized for inhibition of cytokine production

Pentamidine isethionate reduces Ia expression and antigen presentation by Langerhans cells and inhibits the contact hypersensitivity reaction

The mechanism of action of pentamidine isethionate, a diamidino compound used in the treatment of Pneumocystis carinii pneumonia, is unknown. We recently reported that this drug may inhibit the release of inflammatory mediators from alveolar macrophages, which may be associated with its antiparasite activity. As a potential anti-inflammatory agent, we report that topically applied pentamidine reduces ear swelling in the contact hypersensitivity reaction to oxazolone in B6C3F1 mice. The application of pentamidine must occur within 1 h, at the challenge site, to be effective. Topical application appears necessary, because i.v. injection had no effect on reduction of ear swelling. In dose-response studies, a 50% reduction in ear swelling was achieved with as little as 20 \u3bcg of pentamidine. Pentamidine did not affect Ag transport from the challenge site to the draining lymph nodes, as measured by FITC transport. However, there was a 30 to 40% reduction in epidermal cells expressing Ia Ag from pentamidine-treated mouse ears, compared with control. Ia expression is almost exclusively limited to Langerhans cells in the normal epidermis. This reduction in Ia expression was not due to simple depletion of Langerhans cells by pentamidine, because CD45 expression was unaffected. Concurrent with reduced Ia expression, Ag presentation by pentamidine-treated Langerhans cells was also reduced. Taken together, a mechanism of action for pentamidine in inhibition of the contact hypersensitivity reaction appears to be via a reduction in Ag presentation by decreasing Ia+ Langerhans cells

Risk assessment in immunotoxicology. II. Relationships between immune and host resistance tests

We have reported on the design and content of a screening battery using a 'tier' approach for detecting potential immunotoxic compounds in mice (Luster et al., Fundam. Appl. Toxicol., 10, 2-19, 1988). The data base generated from these studies, which consists of over 50 selected compounds, has heen collected and analyzed in an attempt to improve future testing strategies and provide information to aid in developing future quantitative risk assessment for immunotoxicity. In a recent study it was shown that as few as two or three immune parameters were needed to predict immunotoxicants in mice (Luster et al., Fundam. Appl. Toxicol., 18, 200-210, 1992). In particular, enumeration of lymphocyte populations and quantitation of the T-dependent antibody response were particularly beneficial. Furthermore, commonly employed apical measures (e.g., leukocyte counts, lymphoid organ weights) were fairly insensitive. The present analyses focus on the use of this data base to develop statistical models that examine the qualitative and quantitative relationship(s) between the immune function and host resistance tests. The conclusion derived from these analyses are: (1) A good correlation exists between changes in the immune tests and altered host resistance in that there were no instances where host resistance was altered without affecting an immune test(s). However, in some instances immune changes occurred without corresponding changes in host resistance. (2) No single immune test could be identified which was fully predictive for altered host resistance, although most assays were relatively good indicators (i.e., >70%). Several others, such as proliferative response to lipopolysaccharide and leukocyte counts, were found to be relatively poor indicators for host resistance changes. (3) The ability to resist infectious agent challenge is dependent upon the degrees of immunosuppression and the quantity of infectious agent administered. (4) Logistic and standard regression modeling using one extensive chemical data set from the immunosuppressive agent, cyclophosphamide, indicated that most immune function-host resistance relationships followed linear rather than linear-quadratic (threshold-like) models. For most of the relationships this could not be confirmed using a large chemical data set and, thus, a more mechanistically based approach for modeling will need to be developed. (5) Using this limited data set, methods were developed for modeling the precise quantitative relationships between changes in selected immune tests and host resistance tests