Selective early increases of bronchoalveolar CD8+ lymphocytes in a LEW rat model of hypersensitivity pneumonitis.

BACKGROUND: The pathogenesis of hypersensitivity pneumonitis (HP) involves cell-mediated hypersensitivity; various bronchoalveolar T-cell subsets with uncertain roles in disease have been reported and implicated in the pathogenesis. OBJECTIVES: Previous studies at 72 hours after initial antigen challenges showed proportionate increases in T-cell phenotypes. Therefore we tested the hypothesis that early events in response to inhaled antigen in a LEW rat model of HP would include a disproportionate appearance in bronchoalveolar lavage fluid (BALF) and lung parenchyma of a specific T-effector cell responsible for subsequent inflammation and that these events could be identified by phenotyping. METHODS: We double labeled BALF and parenchymal lung lymphocytes with monoclonal antibodies and used flow cytometry to quantitate CD4+ and CD8+ phenotypic subsets 4 and 24 hours after inhalation of antigen. RESULTS: We found disproportionate increases in BALF CD8+ phenotypes. The strongest correlation with pathologic findings was for a putative cytotoxic effector (CD8+CD45R-) T lymphocyte. CONCLUSION: Meaningful interpretation of lung T-cell phenotype quantitation requires studies of kinetics of cellular influxes, timing after antigen challenge, and relative comparison with increases in other phenotypes. Any pathogenetic role assigned to a phenotype must also await functional studies, including cytokine generation and secretion and cell-cell interactions in situ.

Adoptive transfer of experimental hypersensitivity pneumonitis in the LEW rat.

The pathogenesis of immune-mediated pulmonary inflammation following inhalation of antigen in sensitized subjects may involve specific cellular or humoral mechanisms, or both. We used adoptive transfer to document cellular mechanisms in an established LEW rat model of acute hypersensitivity pneumonitis. The optimal protocol utilized sensitized spleen cells cultured for 72 h in the presence of antigen and concanavalin A before intraperitoneal injection of 20 x 10(6) cultured cells into sublethally irradiated recipients. Experimental and control rats were subjected 7 d later to twice daily aerosol challenge for 1 or 3 d and examined 12 h after the last challenge. Histopathology was evaluated in one lung, and the other was lavaged and cells evaluated by flow cytometry for T cell phenotypes (CD4, CD8, and RT6, CD45R subsets). Histopathology and cell numbers for most phenotypes were increased in experimental over controls, but proportions were unchanged. Similar results were obtained in animals evaluated at both 24 and 72 h after initial challenge. Results indicate cellular participation in an established LEW rat model of HP. Significant increases in numbers of T cell phenotypes suggest an important role in pathogenesis, but no single phenotype could be incriminated by disproportionate numbers.

Experimental hypersensitivity pneumonitis in the rat: histopathology and T-cell subset compartmentalization.

The pathogenesis of hypersensitivity pneumonitis (HP) appears to depend largely on T-cell specificity and interactions with monocytes/macrophages. We studied T-cell subset populations, defined by surface membrane markers with putative functional correlates, present in lung parenchyma and bronchoalveolar spaces of sensitized LEW rats following acute and chronic inhalational challenges with antigen. Our initial hypothesis was that the CD4+ RT6- (TDH) subset, the effector cell of delayed hypersensitivity, would dominate in HP lesions and that CD8+ RT6+ (TS) or CD8+ CD45R+ (TS) subsets, constituting putative suppressor T-cell populations, would dominate in lungs of animals with resolving lesions. We found, however, a heterogeneous population involving all eight of the T-cell subsets that were evaluated. Percentages of the RT6+ phenotype diminished as T cells moved from peripheral blood to lung. Dominant numbers of T cells in acute HP included CD8+ RT6- (TCYT) and CD8+ CD45R- (TCYT) subsets, with putative cytotoxic T-cell activity, in addition to CD4+ RT6- (TDH) cells. We did not demonstrate increases in T suppressor cells as the disease waned.

Plasma and urine diketopiperazine concentrations in normal adults ingesting large quantities of aspartame.

In aqueous solution, aspartame can cyclicize to form its corresponding diketopiperazine (3-carboxymethyl-6-benzyl-2,5-diketopiperazine; DKP) and methanol. We measured plasma and urinary concentrations of DKP in samples obtained from six normal adult subjects ingesting 2.2 mg DKP/kg body weight. The DKP was administered as part of a dose of 200 mg aspartame/kg body weight. DKP concentrations in plasma were below the detection limit (less than 1 microgram/ml) of the high-pressure liquid chromatographic method at each time interval after ingestion at which they were measured. Mean (+/- SD) total urinary DKP excreted during the first 24-hr period after dosing was 6.68 +/- 1.30 mg (4.83 +/- 0.23% of the ingested DKP dose). Approximately 44% of the total DKP excreted was excreted in the first 4 hr after dosing.