Lymphocyte predominant cells of nodular lymphocyte predominant Hodgkin lymphoma interact with rosetting T cells in an immunological synapse

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is a subtype of Hodgkin lymphoma with a preserved B-cell phenotype and follicular T helper (T-FH) cells rosetting around the tumor cells, the lymphocyte-predominant (LP) cells. As we recently described reactivity of the B-cell receptors of LP cells of some NLPHL cases withMoraxellaspp. proteins, we hypothesized that LP cells could present peptides to rosetting T cells in a major histocompatibility complex class II (MHCII)-bound manner. Rosetting PD1(+)T cells were present in the majority of NLPHL cases, both in typical (17/20) and variant patterns (16/19). In most cases, T-cell rosettes were CD69(+)(typical NLPHL, 17/20; NLPHL variant, 14/19). Furthermore, both MHCII alpha and beta chains were expressed in the LP cells in 23/39 NLPHL. Proximity ligation assay and confocal laser imaging demonstrated interaction of the MHCII beta chain expressed by the LP cells and the T-cell receptor alpha chain expressed by rosetting T cells. We thus conclude that rosetting T cells in NLPHL express markers that are encountered after antigenic exposure, that MHCII is expressed by the LP cells, and that LP cells interact with rosetting T cells in an immunological synapse in a subset of cases. As they likely receive growth stimulatory signals in this way, blockade of this interaction, for example, by PD1-directed checkpoint inhibitors, could be a treatment option in a subset of cases in the future.