CHALLENGE ASSAY IN-VITRO USING LYMPHOCYTE BLASTOGENESIS FOR THE CONTACT HYPERSENSITIVITY ASSAY

To confirm positivity in routine guinea pig studies, contact allergeni city was investigated by a challenge assay in vitro using a co-culture of autologous lymphocytes passed through a nylon-wool column and anti gen-presenting cells (APCs) modified with or without antigen. Prolifer ation of the lymphocytes primed with ovalbumin and/or 2,4-dinitrochlor obenzene was antigen specific and dependent on the presence of APCs (p eripheral blood monocytes, splenic macrophages and macrophages induced by liquid paraffin). For another nine haptens, primed lymphocytes pro liferated significantly more than control lymphocytes; the stimulation index (SI; ratio between [H-3]methylthymidine ([H-3]TdR) incorporatio n of lymphocytes with antigen-modified APCs and [H-3]TdR incorporation of lymphocytes with APCs not modified by antigen) was 1.6-4.8 in sens itized animals whereas it was about 1.0 in control animals. Sodium dod ecyl sulfate did not cause lymphocyte proliferation. The SI value in v itro was correlated with both the positive rate in vivo (r = 0.736) an d the mean response score in vivo (r = 0.645). Thus, it was possible t o confirm that positivity in routine experiments was a true sign of al lergy. A combination of this assay and short-term animal studies would provide an efficient assessment of the allergic potential of chemical s.