Characterization of chicken lymphocyte subsets separated by peanut agglutinin

The reactivity of chicken lymphocytes isolated from bursa, thymus, spleen, and peripheral blood (PBL) with peanut agglutinin (PNA) has been investigated. High numbers of cells binding PNA (PNA⁺ cells) were found in bursa (74.5%) and thymus (85.2%), as well as in the peripheral organs (spleen and PBL, 43.8 and 70%, respectively). In the latter organs, the levels of PNA⁺ cells exceeded by far the values reported for mammals. Separation of PNA⁺ and PNA^- cells from different organs was achieved by selective agglutination with the lectin or by affinity chromatography on immobilized PNA. Experiments combining the use of limiting concentrations of neuraminidase to cleave off sialic acid from the surface membrane of splenocytes that do not bind PNA (PNA^- cells), followed by agglutination with the lectin, suggested that the high binding of PNA to mature lymphocytes is most likely due to a low degree of sialylation of chicken cell surface glycoconjugates. The functional properties in vitro of PNA⁺ and PNA^- spleen cell fractions were assayed in mitogen responses (PHA, Con A, PWM), the mixed-lymphocyte reaction (MLR), and the in vitro anti-SRBC antibody response. In all three systems the responses of the PNA⁺ fraction were found to be significantly higher than those of the PNA^- cells. Mixing experiments revealed that irradiated (1500 R) PNA^- cells preferably suppress pure T-cell responses of unfractionated spleen cells, whereas PNA^- cells exerted a stronger suppressive effect on responses involving B cells. Thus, in the chicken, PNA may be a valuable tool to distinguish subsets of suppressor cells with different target specificity.