Primary and secondary clonotypes
During the somatic recombination, the two chromosomes recombine independently, and typically this process leads to only one functional gene for each chain type. The second copy of the gene, most often non-functional, can still be expressed and captured by scV(D)J-Seq. Hence, for each cell, it is possible for up to two different copies of the same chain type to be present in a cell:
- Primary: The copy that leads to a productive CDR3. If no productive CDR3s are identified, then the copy with the highest UMI count.
- Secondary: The second copy, if present.
For example:
- If a T cell contains two productive TRB chains, the chain with the highest number of UMIs will be part of the primary clonotype, while the chain with the lowest number will be part of the secondary clonotype.
- If a B cell contains two light chains and only one is productive, the productive chain will be part of the primary clonotype, while the unproductive chain will be part of the secondary clonotype.
The Cell Clonotypes created by the Single Cell V(D)J-Seq Analysis tool only contain primary / secondary clonotypes. Imported clonotypes (see Import Cell Clonotypes) and those produced by Combine Cell Clonotypes (see Combine Cell Clonotypes) can have barcodes with more clonotypes. These additional clonotypes are presented as "Subsequent" and are biologically unlikely. They can be removed using the Filter Cell Clonotypes, see Filter Cell Clonotypes for details.