The H-RS-like cells in infectious mononucleosis are transformed interdigitating reticulum cells.

The lymphoid tissues from patients with infectious mononucleosis or, less frequently, with other reactive conditions may contain Reed-Sternberg (RS)-like cells. These tissues also contain cells resembling the lacunar cells or lymphocytic/histiocytic (L/H) variants, which are present in the lymphocyte-predominant type of Hodgkin's disease. The phenotype of these RS- and L/H-like cells was determined with a large panel of antibodies and lectins. The cells expressed sialylated Leu-M1, Con A, LN-2, and, less frequently, interleukin-1, S-100, and peanut agglutinin receptor. They reacted negatively with two markers for RS cells, Ki-1 and HeFi-1. These RS-like cells were consistently negative for T- and B-cell markers, including immunoglobulins. The markers of the RS-like cells are distinctly different from those in B-immunoblasts, but closely resemble those in interdigitating reticulum cells. It is concluded that interdigitating reticulum cells, when stimulated, can be transformed into lacunar-, L/H-, or RS-like cells.