Use of an optimized in vitro lymphocyte blastogenesis assay to detect contact sensitivity to nickel sulfate in mice

This study was designed to determine whether an optimized in vitro lymphocyte blastogenesis assay for identification of strong contact sensitizers would also detect sensitization to the weaker, clinically relevant allergen nickel sulfate (NiSO4). Though NiSO4 is effective in eliciting allergic skin reactions in patients sensitized to nickel-containing metals, it has been difficult to assess its potential to induce sensitization using standard or developmental in vivo animal tests. In vitro lymphocyte blastogenesis has been useful in the diagnosis of nickel allergy in humans, but has not been applied to predictive testing in animals. We used a previously optimized lymphocyte blastogenesis assay to determine whether lymphocytes from NiSO4-treated mice would exhibit NiSO4-specific proliferation and whether this would correlate with an in vivo ear swelling response. BALB/c mice given repeated open induction applications of NiSO4 were ear challenged, then lymphocytes from the draining nodes were cultured with Langerhans cell-enriched epidermal cells (EC), EC + soluble NiSO4, or NiSO4-modified EC (modified by preincubation with NiSO4). The NiSO4-modified EC stimulated significant NiSO4-specific proliferation. EC + soluble NiSO4 stimulated a nonspecific blastogenic response in lymphocytes from both NiSO4-treated and naive mice. There was no ear swelling response to NiSO4 using standard challenge procedures. However, exaggeration of the challenge procedure by gently abrading the ears just prior to NiSO4 application resulted in significant ear swelling, thereby supporting the conclusion that the in vitro results were indicative of in vivo sensitization.