Splenectomy modulates the immune response but does not prevent joint inflammation in a mouse model of RA

Abstract

The spleen is the largest secondary lymphoid organ which is involved in the development of B cells and also in systemic (auto)immune responses. Here, we investigated the significance of the spleen in the autoimmune arthritis induction and pathogenesis using the recombinant human G1 domain-induced arthritis (GIA) model in splenectomized and control BALB/c mice. Splenectomized mice developed GIA with similar clinical picture to the control group. However, we observed significant alterations in the humoral and cellular immune responses in splenectomized mice. In the sera of the splenectomized mice, we found lower pro-inflammatory cytokine and anti-rhG1 IgM levels, but higher IL-4, anti-rhG1 IgG1 and anti-CCP and RF antibodies. The arthritis induction in the splenectomized group was associated with a significant expansion of activated helper T cells and an increase in the proportion of the circulating B1 and marginal zone B cell subsets. Importantly, immunization of the splenectomized mice with the rhG1 induced the formation of germinal centers in the inguinal- and mesenteric lymph nodes (i/mLNs) which showed active immune response to rhG1. Finally, both B- and T cells from the mLNs of the splenectomized mice showed decreased intracellular Ca 2+ signaling than those of the control group. Collectively, these findings indicate that the presence of the spleen is not critical for the induction of GIA, and in its absence the autoimmune arthritis is most likely promoted through the compensatory activity of the i/mLNs. However, our data implies the immunological role of the spleen in arthritis which could be further assessed in human RA.

Splenectomy at early stage of autoimmune arthritis delayed inflammatory response and reduced joint deterioration in mice

“…three times on days 0, 28, and 56 using the rhG1 antigen (40 μg) mixed with dimethyl-dioctadecyl-ammonium (DDA) adjuvant dissolved in PBS as described [ 14 ]. Arthritis severity and clinical signs were examined throughout the whole experiment every other day using a clinical scoring system as described [ 8 , 14 ]. The diameter of mice paw thickness was measured using a digital caliper.…”

“…During the first phase, after the first immunization, pathological autoantibodies (rheumatoid factor—RF and anti-cyclic citrullinated peptide antibodies—anti-CCP) can already be detected in the serum before the appearance of clinical symptoms [ 8 ]. After that, mild undulating symptoms of inflammation start to develop, resembling the preclinical phase of human RA [ 8 , 13 , 14 ]. In the second phase usually manifested after the second immunization, most mice develop moderate to severe joint inflammation, corresponding to the early phase of clinical RA.…”

“…In addition to serving as a major secondary lymphoid organ, involved in B-cell differentiation and tolerance, hosting memory B cells, and also supporting peritoneal B-cell persistence [ 16–18 ], the spleen is also involved in the development of RA and other autoimmune diseases like systemic lupus erythematosus (SLE) and systemic sclerosis [ 19–22 ]. In our previous study [ 14 ], we reported that splenectomy 4 weeks prior to autoimmune arthritis induction did not alter the clinical picture of GIA [ 14 ]. Splenectomized mice developed RA similar to those of the control (spleen-preserved) group, despite the significant differences in circulating lymphocyte composition and serum parameters [ 14 ] based on which we concluded that the splenectomy led to a complex reorganization of the immune system and other secondary lymphoid organs might have compensated for the absence of the spleen [ 14 ].…”

“…In our previous study [ 14 ], we reported that splenectomy 4 weeks prior to autoimmune arthritis induction did not alter the clinical picture of GIA [ 14 ]. Splenectomized mice developed RA similar to those of the control (spleen-preserved) group, despite the significant differences in circulating lymphocyte composition and serum parameters [ 14 ] based on which we concluded that the splenectomy led to a complex reorganization of the immune system and other secondary lymphoid organs might have compensated for the absence of the spleen [ 14 ].…”

Recombinant Human Proteoglycan Aggrecan‐G1 Domain‐induced Arthritis (GIA) Mouse Model

“…In GIA, significantly greater IL‐17 and IFNγ production by the spleen cells of arthritic mice is observed, together with higher levels of RF and lower levels of anti‐CCP in the serum, as compared to PGIA (Glant et al., 2011). GIA has successfully used in recent years to study the roles of T cell activation and apoptosis (Kugyelka et al., 2019) and different aspects of the spleen's role in autoimmune arthritis (Khanfar et al., 2020; Khanfar et al., 2022; Khanfar et al., 2024).…”