Dual interactions in B cells. (A) Model of dual interactions. Model of “Cellular-partner selectivity” (left). Given molecule A and molecule B (undefined ligand-receptor interacting pair), B cells (illustrated as CD19, gray) express exclusively molecule A on the cell surface and the other cells in their vicinity present molecule B. Prognosis is based on the engaged cell type. Model based on “directionality” of the signaling (right). Given molecule A and molecule B (undefined ligand-receptor interacting pair), the B cell (illustrated as CD19, gray) presents both ligand and receptor molecules. Prognosis is determined by the directionality of the signal upon binding of the complementary molecule, which is expressed by other cells in the surroundings. (B) Proportion of dual interactions established between each possible immune pair under study and their distribution in each prognostic condition. (C) Heat map showing dual interactions with potential targetability in MM. Displayed are the percentage of cells expressing the molecule and the median expression of both molecules by the pair of engaged cell types. Highlighted are those interactions which are significant (P < .05) in 1 condition but not the other. In the shown interactions, the first molecule is expressed in all cases by CD19⁺ cells (B cells); the second molecule is expressed by the 4 cell types (CD3⁺, CD14⁺, CD19⁺, or CD45⁺TN). On the left side of the list of interactions, the column represents TTPlow patients; on the right side, the column represents TTPhigh patients. (D) Model illustrating IL-15–IL-15RA interactions on diverse cell types as example.