Functional Idiotopes: Tumor Antigen–Directed Expression of CD8+ T-Cell Epitopes Nested in Unique NH2-terminal VH Sequence of Antiidiotypic Antibodies?

Antiidiotypic antibodies have been and are being used for cancer immunotherapy based on the rationale that Ab2 carrying an "internal image" of the corresponding tumor antigen can induce tumor antigen-specific antibodies (i.e., Ab3 and inhibit tumor growth). Recent evidence indicates that Ab2 also induces cellular responses by CD4+ and CD8+ T cells. This finding has raised the question of where the short peptides, which express CD8+ T-cell-defined epitopes, are located and their relationship with the tumor antigen. We found that two of the four known Ab2 associated with tumor antigen, with known amino acid sequence, express unique NH2-terminal V(H) sequences which precede the framework regions. Both the unique and the shared NH2-terminal V(H) sequences are nested MHC class I antigen-binding peptides. These peptides were highly homologous with peptides from corresponding tumor antigen (carcinoembryonic antigen, CD55, and human high molecular weight melanoma-associated antigen) but differed from the tumor antigen peptides by the presence of the side chain known to mediate stronger forces of interaction with other atoms. The presence of candidate CTL epitopes in NH2-terminal V(H) of Ab2 homologous with tumor antigen may be important for the development of novel immunotherapeutic strategies for cancer.

T cell receptor-gamma gene analysis of CD30+ large atypical individual cells in CD30+ large primary cutaneous T cell lymphomas

The hallmark of primary cutaneous CD30+ large T cell lymphoma are large lymphoid tumor cells, at least 75% of which, by definition, must be positive for CD30. The relatively benign clinical course of this lymphoma type has been explained with CD30-induced apoptosis, on the assumption that expression of CD30 defines the tumor clone; however, this hypothesis has not been tested on the molecular level to date. In this study we analyzed CD30+ cells in four patients with primary cutaneous CD30+ large T cell lymphoma by single cell polymerase chain reaction of T cell receptor-gamma genes followed by sequencing. Here, we demonstrate that most of the large CD30+ atypical cells possessed identical T cell receptor-gamma gene rearrangements, indicative of clonal proliferation. Nevertheless, polyclonally rearranged T cells were present in all CD30+ samples studied. In addition, one patient showed a second clone in a separate biopsy and three of four patients showed chromosomal imbalances as revealed by comparative genomic hybridization. Taken together, our data suggest that the CD30+ population in primary cutaneous CD30+ large T cell lymphoma indeed contains the tumor clone, thus providing molecular support for a link between clinical course and CD30-related signaling. Importantly, however, CD30 expression does not define the tumor clone as bystander T cells, as well as occasional additional clones, are also present in this population.