I wouldn’t refer to ideals but to the fact that reciprocity is a key factor from the smallest cells to human organisms.
In cell-to-cell communication and gene expression, ‘reciprocal’ usually refers to the coordinated, opposite or complementary expression patterns of two cells during communication. For example, one cell may express a ligand, while the other expresses its matching receptor, meaning the signal sent by one cell is ‘received’ by the other.
More specifically, single-cell transcriptomics can reveal pairs of cell types in which one is ligand-high and the other is receptor-high, suggesting a directional interaction between them. This relationship is ‘reciprocal’ not because both cells perform the same function, but because their respective roles complement each other: sender and receiver, or signal and response.
Cells can switch identity or adopt new roles through reprogramming, differentiation or transdifferentiation, particularly in response to changes in their environment or gene regulatory state. A cell does not always remain fixed in the role it first had. Some cells can be pushed into a different lineage, and some differentiated cells can partially or fully take on functions belonging to another cell type. For example, in experiments, thymus-derived epithelial cells were reported to contribute to skin function after implantation, demonstrating that cells can adapt to a new tissue environment by altering their genetic programme and functional role.
Cell-to-cell communication helps to drive this process. Signals from neighbouring cells can alter which genes are activated or inhibited, enabling a cell to gradually transition from one state to another under the influence of its surroundings. During development and repair, this is one way in which a cell can ‘learn’ a new function: the tissue context instructs it through ligands, receptors and changes in gene expression.