Antigen specific IgE responses originate in gut associated lymphoid tissue (GALT) of mice sensitized with benzylpenicilloyl-keyhole limpet hemocyanin (BPO-KLH) in alum, regardless of the route (intraperitoneal [i.p.], oral [gavage], subcutaneous [s.c.], intramuscular [i.m.] or intravenous [i.v.]) used for immunization. When BALB/c mice were injected i.p. with BPO-KLH (10 micrograms) in alum, B lymphocytes bearing membrane bound IgE (sIgE+B cells) first appeared simultaneously in Peyer's patches (PP) and mesenteric lymph node (MLN) on day 8. BPO specific IgE antibody forming cells (AFC) also appeared in PP on day 8, but were not found in MLN until day 10. On day 8, no sIgE+B cells or IgE AFC were found in bone marrow (BM) or other lymphoid organs. The appearance of sIgE+B cells and IgE AFC in PP and MLN was transient; these cells were no longer detected in PP on days 14 and 24, respectively, or in MLN on days 14 and 36, respectively. sIgE+B cells and IgE AFC did not appear in spleen until day 12, where they were detected through day 70. Although sIgE+B cells were never found in BM, IgE AFC appeared in BM on day 18, where they were detected through day 70. No sIgE+B cells or IgE AFC were found in other lymph nodes (OLN) on days 0-70. Boosting did not induce the reappearance of sIgE+B cells or IgE AFC in PP, the reappearance of sIgE+B cells in MLN, the appearance of sIgE+B cells in BM, or the appearance of sIgE+B cells or IgE AFC in OLN.(ABSTRACT TRUNCATED AT 250 WORDS)