Antigen localization in lymphopenic states. I. Localization pattern following chronic thoracic duct drainage.

Adult rats, depleted of thoracic duct lymph for 5–7 days, were tested for their ability to localize I-labelled polymerized flagellin from . Labelled antigen was injected into both hind footpads 6–12 hours after completion of drainage, and the regional nodes were excised 24 hours later. Grain counts on identically exposed autoradiographic sections from regional nodes were used to assess differences in antigen distribution between depleted and nondepleted rats. The uptake of antigen by medullary macrophages was no different in the two groups. However, the uptake of antigen by primary lymphoid follicles was reduced by thoracic duct drainage to levels one-fourth that observed in normal rats. Two procedures were found capable of improving follicular antigen uptake in the chronically depleted rat: (1) regional inoculations of 0.01 ml of specific antiflagellar immune serum at a titre of 1:400 1 hour prior to antigen injection, and (2) daily return by intravenous infusion of washed autogenous thoracic duct lymphocytes collected during drainage. Regional injections of both viable and non-viable lymphocytes were ineffective in improving follicular antigen uptake in the depleted animal. The results show that depleted rats lack a serum factor, presumably an opsonin, important in determining antigen distribution patterns. It seems likely that this factor is normally manufactured by small lymphocytes.