They recirculate constantly through secondary lymphoid tissues in search of antigen. If they encounter antigen, they stay in the lymphoid tissue and initiate a specific immune response. If they do not encounter antigen, they leave the lymphoid tissue and continue recirculating throughout the body. After this, progeny of the original cell leave the lymphoid tissue and may recirculate. Memory cells home to the type of tissue in which they first encountered antigen.
Cells also enter secondary lymphoid tissues through the lymphatics.
Factors released by various cells during an inflammatory response which trigger or enhance the inflammatory response. Over 50 identified to date. Classified according to the arrangement of conserved cysteine residues. Beta chemokines tend to not attract neutrophils, but instead attract monocytes, eosinophils, basophils and lymphocytes with variable selectivity. N-terminal amino acids influence the selectivity of the chemokines for specific leukocyte subsets.