Mast cell degranulation as a major event in the effector phase of delayed-type hypersensitivity induced by cloned helper T cells

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Isolation and synthesis of a novel immunosuppressive 17alpha-substituted dammarane from the flour of the Palmyrah palm (Borassus flabellifer)

The novel triterpene 1 with a dammarane skeleton and a hitherto unknown 17alpha-substitution pattern has been isolated from the Palmyrah palm in low yield and prepared by synthesis in larger quantities. 1 was shown to be an extremely potent immunosuppressant in vitro (MLR; IC50 = 10 ng/ml) and in vivo (DTH; ED50 = 0.01 mg/kg p.o.). A glucocorticoid like activity is excluded.

Serum histamine and the elicitation of murine contact sensitivity

We report that challenge of previously contact-sensitized mice results in a significant increase in the concentration of serum histamine. In an attempt to determine whether this phenomenon might form the basis of an alternative method for the evaluation of elicitation reactions in experimental contact sensitivity, we have compared challenge-induced increases in ear thickness with elevations in serum histamine. Challenge of sensitized mice revealed that both ear thickness changes and increases in the serum level of histamine were dependent upon the concentration of oxazolone used for sensitization. The kinetics of changes in serum histamine concentration were found to be biphasic, with a small increase measurable 2 h following challenge and the maximal response at 24 or 48 h. In contrast, increases in ear thickness were monophasic, although maximum responses were also observed at 24 h. It is concluded that, although they do not exactly parallel increases in ear thickness, changes in histamine concentration may provide a useful serological correlate of the challenge reaction in contact sensitivity.

Lymphocyte activation by house dust allergen in asthma: analysis with monoclonal antibodies

Peripheral blood mononuclear cell (MNC) response to house dust (HD) stimulation in cultures was studied in a group of 35 subjects with asthma and a multiple positive skin test (ST) reaction to inhalant allergens including HD, and in 19 healthy controls. The MNC response to allergen stimulation was assessed by interleukin-2 receptor (IL-2R) expression identified with an anti-Tac monoclonal antibody. Lymphocyte subpopulations of baseline and cultured cells were also analysed. The percentage of IL-2R presenting cells increased significantly in HD-driven cultures in the asthma group compared to controls. The increase in proportion of IL-2R+ cells was closely related to the increase in CD4+ percentage of cultured cells and was accompanied by a decrease in proportion of CD8+ lymphocytes and monocytes/macrophages, suggesting that HD-activated cells were CD4+ lymphocytes. Lymphocyte activation, measured by IL-2R expression, was significantly higher in the group of asthmatics, and positive dual (early and late) skin reaction to HD, as compared to those with single early reaction.