Transfer of immunity to Ostertagia circumcincta and IgA memory between identical sheep by lymphocytes collected from gastric lymph

Sheep rendered immune to Ostertagia circumcincta were challenged with 50,000 larvae and lymphocytes were collected from the gastric lymph up to eight days after challenge. The cells were transferred intravenously to genetically identical worm-free sheep which, together with controls, were challenged with 50,000 larvae and killed nine days later. Cells obtained during the donors lymphoblast response to challenge transferred partial immunity, measured either as stunting or loss of worms. Significantly less immunity was transferred by cells collected either before or after this response. Thus the responding cells can mediate protective immunity to O circumcincta. On the other hand the donor sheep remained immune to their challenge infection despite being depleted of these functional cells, showing that their presence was not essential for immunity to be maintained. Comparison of the immunoglobulin A (IgA) concentrations in the gastric lymph of recipient and control sheep showed that a local IgA response had also been transferred. Enumeration of mucosal mast cells suggested that a mastocytosis had been transferred to the two recipients which were most immune to challenge.