Chemokine receptors (CCRs) are a superfamily of surface G protein-coupled receptors with seven transmembrane domains found mainly in leukocytes. CCRs control immune cell behavior and promote chemotaxis, cell adhesion as well as many other biological functions, some of which remain to be discovered. Generally, there are two types of CCRs: conventional chemokine receptors and atypical chemokine receptors (Bachelerie et al., 2014, Rot and Von Andrian, 2004). Conventional CCRs (also known as cCKRs) are the most studied since they directly bind and control the chemokines. On the other hand, atypical CCRs (or aCKRs) are co-expressed in cells with conventional CCRs, indirectly controlling the interaction between chemokines and conventional CCRs.

The conventional CCR superfamily is divided into four classes based on the chemokine/ligand interaction motif to which they bind (CC, CXC, CX3C, or XC). CC chemokine receptor family includes 12 members named ordered from CCR1 to CCR12. CXC chemokine receptor family includes CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, CXCR7 and CXCR8. CX3C chemokine receptor (CX3CR1) and XC chemokine receptor (XCR1) are single members of their respective CCR families.

The most studied function of the chemokine network is cell migration. However, a wide variety of other biological processes can be induced by the activation of CCRs on immune cells, including cell proliferation, cell survival and differentiation, cytokine production, endocytosis, degranulation, and antimicrobial activity among many others (López-Cotarelo, Gómez-Moreira, Criado-García, Sánchez, & Rodríguez-Fernández, 2017).

The production of new lymphocytes, also known as lymphopoiesis, takes place in specialized lymphoid primary lymphoid tissues, which are bone marrow and thymus. The antigenic receptor repertoires of T and B cells are shaped in primary lymphoid tissues, but the interaction with antigens and establishment of a diverse clonal repertoire happen in the secondary lymphoid tissues, which are spleen, lymph nodes and mucosa-associated lymphoid tissue (MALT). CCRs are mainly present in lymphocytes and their expression drives the development and homeostasis of different immune cells of all lymphoid organs and behind. In this chapter, we will review the expression of CCRs in the different lymphoid organs, including bone marrow, thymus, spleen, lymph nodes and Peyer’s patches.