The Human D region as a multigene family

Induction of various HLA class II molecules in a human colonic adenocarcinoma cell line

The colonic carcinoma cell line HT-29 had no constitutive expression of HLA class II molecules. Gamma interferon (IFN-gamma) induced expression of HLA class II molecules in a dose-dependent manner with 100 U/ml as an optimal dose. The expression of HLA-DR, HLA-DP, and HLA-DQ molecules seemed to follow different kinetics. While DR and DP molecules were maximally induced after 2 days, DQ molecules appeared later with maximum percentage positive cells after 8 days. Treatment with a prostaglandin synthesis inhibitor (indomethacin) neither induced class II expression nor altered the dose-response curve for IFN-gamma; this indicated that possible endogenous production of prostaglandins in this cell line did not interfere with its class II expression. The lectins phytohaemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM), and wheat germ agglutinin (WGA) did not induce class II expression.

Evaluation of in vitro predictive tests for irritation and allergic sensitization

Investigations of in vitro procedures to predict the potential of substances as skin irritants and as allergens inducing delayed hypersensitivity (contact dermatitis) are described, with indications of possible advances and known limitations. The examination of keratome slices of skin for release of enzymes, for changed histochemistry and for utilization of radioisotope-labelled amino acids will detect weak irritants but is of doubtful value for moderate irritants and will detect corrosive substances only through their inhibition of all cell activities. Fibroblast cultures, tested with Clostridium perfringens toxin and chemicals, show similar limitations in detecting moderate or severe irritants. Fibroblast cultures can be made more relevant to epidermal exposure by an overlying layer of agar containing keratin. In vitro tests to detect induction of sensitizing potential for delayed hypersensitivity have made little progress. The most promising approach is to treat antigen-presenting Langerhans cells with antigen and co-culture with lymphocytes. The lymphocytes may be examined for changes in receptor expression, for synthesis of interleukin 2, and possibly for responses to allergen if sufficient cells become specifically sensitized. There are several in vitro techniques to detect responses of in vivo- or in vitro-sensitized lymphocytes treated with antigen.