Lymphocytes are white blood cell prodominantly found in the lympth glands. Lymphocytes each only present 1 type of antigen-receptor protein on their surface, and these can bind to only 1 specific antigen. This is becuase each lymphocyte is part of a clone (identical cells from the same common ancestral cell), all exhibiting the single type of antigen receptor.
The lympth fluid travels around the body via lympth glands, lymphocytes are therefore able carry out immune survallience, by recongising protein partcles. Lymphocytes recongise antigens by distinct differences in the protective protein coats of forgein bodies, from somatic cells.
If the specific lymphocyte clones antigen-receptor recongines and binds to an antigen then the lymphocyte undergoes clonal selection. The activation of the lymphocytes makes them divide rapidly to produce many more clones, with the same antigen receptor.
 Medical News Today. (2018, Feb). What are lymphocytes and what are healthy levels to have? Joana Cavaco Silva. Available at: https://www.medicalnewstoday.com/articles/320987.php (Accessed: 2.12.18)
 Science Direct. (1998). Clonal Selection. Clonal Selection. Norman R.Klinman. Available at: https://www.sciencedirect.com/science/article/pii/B0122267656001596 (Accessed 2.12.18)