The long-term collection of lymph from single lymph nodes of foetal lambs in utero.

Surgical techniques are described for the long-term collection of lymph from both prescapular efferent lymph ducts of foetal lambs in utero. Lymph ducts in foetal lambs 95 to 136 days post-conception were cannulated with a high rate of success. Lymph flow from the cannulas was not compromised by deliberate primary or secondary challenge of the lymph nodes with a wide variety of antigens, and often continued for long periods after the lambs were born naturally. The techniques allow cellular and humoral lymph-borne immune responses of foetal lambs to authentic primary antigenic challenge to be studied in utero, uncomplicated by any previous experience of antigens. Loss of lymphocytes from the cannulated ducts depleted the numbers of cells in the lymph, but lymph protein concentrations were unaffected by lymph drainage.