Reevaluation of inguinal lymph node injection for production of adjuvant arthritis in the rat

An experiment was designed to compare the efficiency of lymph node injection for the induction of adjuvant arthritis (AA) with that of conventional footpad injection in the rat. Quantitative studies revealed that the minimal dose required for induction of AA by the lymph node route is one fifth of that by the footpad route. Thus, the lymph node route was found to be more efficient than the footpad method in terms of higher incidence and earlier onset of AA. PPD in Freund's incomplete adjuvant was able to produce tuberculin sensitization in the rat. The lymph node route again proved to be superior in terms of consistent appearance of the 24-hour reaction on days 8 and 14 and prolongation of the skin reaction over 48 h. These findings show that the lymph node method is so efficient in the rat that it will be especially useful for the trial induction of AA with various materials of unknown potency as well as for production of delayed hypersensitivity. In addition, this injection method appears to be a simple and efficient technique for assay of other immunological reactions.