Abundance and nuclear antigen reactivity of intestinal and fecal Immunoglobulin A in lupus-prone mice at younger ages correlate with the onset of eventual systemic autoimmunity

Abstract

Our recent studies, using (SWRxNZB)F1 (SNF1) mice, showed a potential contribution of the gut microbiota and pro-inflammatory immune responses of the gut mucosa to systemic autoimmunity in lupus. Here, using this mouse model, we determined the abundance and the nAg reactivity of IgA antibody produced in the intestine under lupus susceptibility. Intestinal lymphoid tissues from SNF1 mice, females particularly, showed significantly higher frequencies of nAg (dsDNA and nucleohistone) reactive IgA producing B cells compared to B6 females. Most importantly, younger age fecal IgA -abundance and - nAg reactivity of lupus-prone mice showed a positive correlation with eventual systemic autoimmunity and proteinuria onset. Depletion of gut microbiota in SNF1 mice resulted in the diminished production of IgA in the intestine and the nAg reactivity of these antibodies. Overall, these observations show that fecal IgA features, nuclear antigen reactivity particularly, at preclinical stages/in at-risk subjects could be predictive of autoimmune progression.

Preclinical stage abundance and nuclear antigen reactivity of fecal Immunoglobulin A (IgA) varies among males and females of lupus-prone mouse models

“…Importantly, anti-DNA antibodies of IgA class are found in the serum of patients with SLE [18][19][20][21][22][23]. These reports along with our studies [13,14,24] showing pro-inflammatory immune phenotype and higher plasma cell frequency in the intestine, and higher abundance and nAg reactivity of fecal IgA in female SNF1 mice at preclinical stages suggested that the degree of IgA secretion in the gut lumen could be indicative of systemic autoimmune progression. However, whether these features are unique to SNF1 mice or ubiquitous to other preclinical models of lupus [such as MRL/lpr, NZM2328, NZM2410, (NZBxNZW-F1) NZB/WF1] is not known.…”

“…We also examined if fecal IgA features at younger ages show a correlation with the eventual nAg reactivity of serum IgG in males and females. We found that fecal IgA in MRL/lpr, NZM2328, NZM2410, NZB/WF1 mice, similar to SNF1 mice [14], shows varying degrees of age dependent increase in the abundance and nAg reactivity. Fecal IgA in these mice showed considerable levels of nAg reactivity starting at as early as juvenile age.…”

“…Using a slow progressing lupus-prone mouse model, (SWRxNZB)F1 (SNF1) strain, we showed a potential contribution of gut microbiota and pro-inflammatory immune response initiated in the gut mucosa in triggering the disease associated gender bias in SLE [12,13]. We also reported that the preclinical stage IgA production in the gut, and the abundance and nuclear antigen (nAg) reactivity of fecal IgA are correlative of the onset of anti-nAg seropositivity and the eventual proteinuria, and gender bias of the disease incidence in SNF1 mice [14].…”

“…Antibody titers against nAgs [(double stranded DNA (dsDNA) and nucleohistone (NH)] in mouse sera and fecal extracts were assessed by ELISA as described in our recent reports with minor modifications [9,[12][13][14]. Briefly, 0.5g/well of nucleohistone (Sigma-Aldrich) in carbonate buffer or 0.5g/well dsDNA from calf thymus (Sigma-Aldrich) in 50% DNA coating solution (Thermo) + 50% PBS was coated as nAg onto ELISA plate wells.…”

“…Proteinuria: Urine samples were tested at regular intervals, as early as at 12 weeks of age, to detect proteinuria and confirm the previously reported trends in disease incidence in different strains of lupus-prone mice from our facility. Protein level in the urine was determined by Bradford assay (BioRad) against bovine serum albumin standards as described before [9,13,14]. Mice that showed proteinuria (>5 mg/ml) were considered to have severe nephritis or clinical stage disease.…”