The jawless vertebrates like lamprey and hagfish have an adaptive immunity which is very similar to the one of the jawed vertebrates. There is an T-/B-Cell like lymphocyte lineage. Therefore these cells are called lymphocyte like cells (LLC). They are distinguished through the expressed receptor into the three subclasses:
Antigen receptors
The expressed receptor is the so-called variable lymphocyte receptor (VLR), which belongs to the leucine-rich repeat (LRR) family.
References
Adaptive immunity in jawless vertebrates Wikipedia(Text) CC BY-SA