Studies on Transplantation Antigen Extracts in Syrian Hamsters

A polyoma virus-induced CB strain hamster tumour has been defined with regard to its immunogenetic specificity (section 3.1) and evaluated as a convenient source of cells from which a crude but biologically active, strain-specific 'transplantation antigen' can easily be prepared. This antigen is resistant to repeated freezing and thawing, lyophilization and subsequent storage at 5 degrees C (section 3.3). Although the extracted antigen elicited 'direct hypersensitivity' reactions when inoculated intracutaneously into MHA strain hamsters specifically presensitized against CB tissue antigens by means of skin homografts or lymphoid cellular inocula, it was incapable of inciting transplantation immunity in normal MHA hosts. However, when emulsified in complete Freund's adjuvant and injected into the footpads of MHA recipients, the material was immunogenic as evidenced by (a) their accelerated rejection of subsequent test tumour or skin homografts, (b) their prompt rejection of skin homografts hitherto sustained in a privileged site, and (c) their capacity to give direct reactions when challenged intracutaneously with cells or antigen extract from CB strain donors (section 3.4). Exposure of normal MHA lymphoid cells to CB antigen in vitro altered their behaviour in such a way as to suggest a prompt transformation to an 'immune' or specifically activated status-such cells, after careful washing, were capable of inciting 'immune lymphocyte transfer' reactions in the skins of MHA and (MHA $\times $ CB) F$_{1}$ hosts. However, various findings leave open the possibility that the sensitization actually took place in the skin of the host animal into which the cells were transferred after their exposure to the antigen in vitro (section 3.7). Chronic treatment, over a 90-day period, of adult MHA hamsters with CB antigenic material administered intracutaneously and intraperitoneally, without adjuvant, induced a high degree of tolerance in respect of subsequent homografts of CB skin (section 3.8).