Clonality (from Greek κλών , branch, womb) is a term that describes the origin of cells or their products. If all cells of a population go back to a single common mother cell, one speaks of a monoclonal (or simply clonal ) population. If there are genetic differences and the population can therefore be traced back to several cell lines , then one speaks of a polyclonal population, if there are only a few cell lines of an oligoclonal population.
Individual cell products can also be meant by clonality. Monoclonal antibodies are produced by a cell line that can be traced back to a single B lymphocyte and are thus all directed against a single epitope . In nature, however, antibodies are always produced by different cell lines and are therefore polyclonal .
It is important to determine the clonality of cells, especially in pathology, in the context of assessing the dignity of tumors , since the dignity can usually be inferred directly from the clonality . If, for example, the cells from a biopsy of a breast tumor are compared with those from axillary lymph nodes and it is established that the genomes are the same (e.g. by means of Southern blot analysis), it can be assumed that the cells are of the same origin. are monoclonal, and are therefore malignant tumor cells ( cancer cells ) that have metastasized from the breast into the lymph nodes .