CXCL13 and CCL21 play a key role in ectopic lymphoneogenesis in Sjögren's syndrome

Objective

The aim of this study was to characterise the organisation of neolymphoid structures in glands of patients with Sjögren's syndrome and to correlate their maturation with CXCL13 and CCL21 expression.

Methods

Salivary-gland biopsies from 28 patients with SS and 12 with sialoadenitis were examined using immunohistochemistry (IHC). Infiltrates were characterised according to the score (grade 1, <50 periductal lymphocytes; grade 2, >50 lymphocytes; grade 3 = grade 1 or 2 plus GC). Follicular maturation was assessed with respect to T/B-cell segregation, CD45RO and CD45RA, CD21⁺ FDCs, GC and MECA79⁺ HEVs. CXCL13 and CCL21 expression was also assessed.

Results

Grade 1 showed predominance of CD3⁺/CD45RO⁺ infiltrating lymphocytes. Grade 2 showed increased number of CD20⁺/CD45RA⁺ and a variable degree of organization (54.55% not segregated, 21.21% atypically segregated, 24.24% segregated). Grade 3 showed CD20⁺/CD45RA⁺ predominance with typical segregation. Within grades 2 and 3, we detected CD21⁺ FDC clusters. MECA79⁺ vessels were detected on the edge of the aggregates. CXCL13 expression was detected in 4.07% of grade 1, 46.16% of grade 2 and 100% of grade 3 aggregate and in some infiltrated ducts. CCL21 expression was detected in 2.5% of grade 1, 17.85% of grade 2 and 47.62% of grade 3 aggregates.

Conclusions

The presence of fully formed lymphoid follicles characterized by GC, B/T segregation, HEVs and FDCs within the target organs for SS, and the association of these structures with chemokines acting as regulator of lymphoneogenesis, suggest a key role of these molecules in the pathogenesis and evolution of the disease process.