A modification of the standard fusion methodology is described which results in greatly increased yields of monoclonal antibodies against certain organ-specific parasites. Several fusions were carried out using mice infected with Schistosoma mansoni or Nematospiroides dubius, using B lymphocytes harvested from either the spleen or the mesenteric lymph nodes. Results indicated a greatly improved yield of positive clones using the lymph nodes as a source of B cells for fusion. A 7-fold increase in the number of positive clones was seen with N. dubius injections, while S. mansoni fusions showed a 2-fold increase.