Duck lymphocytes. I. Purification and preliminary observations on surface markers.

High yields of lymphocytes were obtained by centrifuging duck blood, collected into an equal volume of heparinized phosphate-buffered saline, over Ficoll-diatrizoate, sg. 1.077, for 25 min at 200 X g. These lymphocytes did not form E rosettes under a variety of conditions, or EA rosettes with sheep erythrocytes sensitized with rabbit antibodies. High proportions (50-80%) of blood and organ (thymus, bursa of Fabricius, spleen, cervical lymph node) lymphocytes had surface immunoglobulin (SmIg). The proportion of blood lymphocytes with SmIg was reduced (to 16-73%) by previous incubation in serum-free medium; less reduction occurred after similar incubation of organ lymphocytes. With or without previous treatment with neuraminidase duck lymphocytes did not express receptors for Helix pomatia lectin. However, some untreated lymphocytes did have receptors for peanut agglutinin (PNA) and the number was increased after desialation. The proportions and organ distribution of lymphocytes with SmIg or receptors for PNA did not follow a pattern consistent with any expected distribution of T and B cells. Duck blood lymphocytes were separated into 2 bands (mean densities 1.026 and 1.068 g/cm3) in Percoll gradients. These did not differ in expression of SmIg and receptors for PNA, but only the upper band (sg. 1.026) responded to phytohaemagglutinin, concanavalin A, pokeweed mitogen and rabbit anti-duck immunoglobulin serum in lymphocyte transformation tests. Blood lymphocytes were also separated according to their adherence to nylon wool. There was no difference in surface markers between the adherent and non-adherent cells, but only the adherent population responded to mitogens. It is suggested that since ducks are phylogenetically close to the amphibians and reptiles their lymphocyte populations may not express surface markers similar to those of chickens and mammals.