Final answer:
The statement about naive lymphocytes using CCL18 and CXCL13 to enter Peyer's patches is false; instead, they are primarily attracted by CCL19 and CCL21, although CXCL13 is involved in B cell follicle organization.
Step-by-step explanation:
The statement that naive lymphocytes can enter Peyer's patches through high endothelial venules (HEVs) following the chemokine gradient of CCL18 and CXCL13 is false. Naive lymphocytes indeed use HEVs to enter lymphoid tissues, but the chemokines responsible for attracting naive lymphocytes to Peyer's patches are primarily CCL19 and CCL21, not CCL18 and CXCL13. CXCL13 does play a role, but it is primarily involved in the organization of B cell follicles within lymphoid tissues such as Peyer's patches.