Spontaneous rosette-forming cells in the chicken. Tissue distribution, binding characteristics and bursa dependency.

The frequency and binding characteristics of cells spontaneously forming rosettes (RFC) with rabbit erythrocytes (RRBC) and sheep erythrocytes (SRBC) in different tissues of 6-week-old chickens were studied. RFC were most frequent in the bursa of Fabricius, followed in order by the spleenpquent than SRBC-RFC. The number of erythrocytes (RBC) bound by each RFC was also determined. The mean binding capacity of the RFC for either RRBC or SRBC did not differ between the different tissues. The distribution of the RFC into classes binding different numbers of RRBC was similar for all analysed tissues. Howeverthe corresponding distribution for the SRBC-RFC was considerably more heterogeneous. Embryonic surgical (S-Bx) or cyclophosphamide (Cy-Bx) induced bursectomy much reduced the frequencies of RFC binding SRBC in the spleen. The frequency of RRBC-RFC was not altered by these procedures. S-Bx reduced the frequency of spleen RFC binding lightly but not heavily trinitrophenyl-haptenized (TNP) SRBC, whereas Cy-Bx reduced the frequency of the latter RFC type.