Homotypic cluster formation of dendritic cells, a close correlate of theirstate of maturation. Defects in the biobreeding diabetes-prone rat

Aggregation of dendritic cells (DCs) in homotypic clusters has been describ ed in vivo in lymph and shin, and here we report studies on homotypic clust ering of rat splenic (s) DCs in vitro. Wister rat sDCs readily formed homot ypic clusters in culture, which increased in number and size over time (wit h a peak at t = 3 h). Keeping the cells at higher densities or treatment wi th anti-CD43 induced more and larger homotypic clusters, After such enhance d clustering the DCs had increased their T cell stimulating capabilities in syngeneic mixed lymphocyte reaction, and had a higher expression of CD80 a nd CD86 (signs of maturation). Ag transfer from bovine serum albumin-fluore scein isothiocyanate-pulsed to unpulsed DCs was observed during clustering. Here we also show that sDCs of the biobreeding diabetes-prone (BB-DP) rat, a model of autoimmune diabetes/thyroiditis, formed fewer and smaller clust ers than Wistar sDCs, and that DC-DC clustering resulted in only a modest m aturation of the cells (as determined in syn MLR and by phenotyping). Anti- CD43 completely restored the clustering defect BB-DP DCs in vitro, yet T ce ll-stimulating capability was only restored to a limited extent. Ag transfe r in BB-DP DC clusters was similar.