MEASUREMENT OF GRAFT-VERSUS-HOST REACTIONS ON THE CHORIOALLANTOIC MEMBRANE OF THE CHICKEN

Abstract

Focal opacities or pocks form on the chorioallantoic membrane after inoculation with competent lymphocytes. Minor B_o and major B histoincompatibilities can be discriminated by the sizes of the pocks (mean diameters of 0.32 and 1.02 mm). The number of minor B_o pocks is directly proportional to graft-versus-host splenomegaly. The blood of donors differ greatly as initiators of large B pocks (from 1 to 5/mm⁸ of whole blood). This variation is associated with the B genotype of the donor but appears to be independent of the B genotype of the embryo. The number of large B pocks is reduced by X-irradiation or Mitomycin-C treatment of donor cells. The D_o for X-irradiation is 94 R, identical with the D_o for the suppession of haematopoietic colony-forming units, and the LD₅₀ for Mitomycin-C, under standard conditions, is 6.3 µ/ml. Dilution of the inocula reduces the number of large pocks in direct proportion to the reduction in cell number. Neither genetic selection of the donor nor any of the treatments reduce the size of the pocks or delay their appearance. This indicates that each pock probably marks the site of an antigen-initiated proliferation of a single donor lymphocyte, entraining thereby the pathological changes which culminate in the formation of a visible pock.