Carole L. Galligan

Sex affects immunity.

Sex based differences in immune responses, affecting both the innate and adaptive immune responses, contribute to differences in the pathogenesis of infectious diseases in males and females, the response to viral vaccines and the prevalence of autoimmune diseases. Indeed, females have a lower burden of bacterial, viral and parasitic infections, most evident during their reproductive years. Conversely, females have a higher prevalence of a number of autoimmune diseases, including Sjogrens syndrome, systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritis (RA) and multiple sclerosis (MS). These observations suggest that gonadal hormones may have a role in this sex differential. The fundamental differences in the immune systems of males and females are attributed not only to differences in sex hormones, but are related to X chromosome gene contributions and the effects of environmental factors. A comprehensive understanding of the role that sex plays in the immune response is required for therapeutic intervention strategies against infections and the development of appropriate and effective therapies for autoimmune diseases for both males and females. This review will focus on the differences between male and female immune responses in terms of innate and adaptive immunity, and the effects of sex hormones in SLE, MS and RA.

Fibrocyte activation in rheumatoid arthritis

OBJECTIVES RA is a common, relapsing autoimmune disease primarily affecting the joints. Fibroblast-like synovial (FLS) cells are thought to be responsible for pannus formation and secretion of factors that recruit leucocytes to affected joints, thereby promoting bone and cartilage destruction. Fibrocytes are multipotent circulating stem cells that may have a role in RA pathogenesis, perhaps as the precursors of the FLS cells, or by regulating FLS cell function. METHODS We utilized multidimensional phospho-specific flow cytometry to characterize the activation status of peripheral blood (PB) fibrocytes derived from human RA patients at different stages of disease and from mice with CIA. RESULTS Human PB fibrocytes from RA patients exhibited phosporylation activation of the p44/42 and p38 MAP kinases (MAPKs), and STAT3 (signal transducer and activator of transcription) and STAT-5 early in disease, within the first year of diagnosis. Similarly, in murine CIA, an increase in the total number of PB phosphoSTAT5-positive fibrocytes was observed at early time points in disease. Notably, in the affected paws of mice with CIA, we identified an increased number of fibrocytes, in contrast to the paws of control mice. CONCLUSIONS These data suggest that activated fibrocytes may influence the disease process in RA and may serve as surrogate markers for disease in the PB of affected patients.

Multiparameter Phospho-Flow Analysis of Lymphocytes in Early Rheumatoid Arthritis: Implications for Diagnosis and Monitoring Drug Therapy

Background The precise mechanisms involved in the initiation and progression of rheumatoid arthritis (RA) are not known. Early stages of RA often have non-specific symptoms, delaying diagnosis and therapy. Additionally, there are currently no established means to predict clinical responsiveness to therapy. Immune cell activation is a critical component therefore we examined the cellular activation of peripheral blood mononuclear cells (PBMCs) in the early stages of RA, in order to develop a novel diagnostic modality. Methods and Findings PBMCs were isolated from individuals diagnosed with early RA (ERA) (n = 38), longstanding RA (n = 10), osteoarthritis (OA) (n = 19) and from healthy individuals (n = 10). PBMCs were examined for activation of 15 signaling effectors, using phosphorylation status as a measure of activation in immunophenotyped cells, by flow cytometry (phospho-flow). CD3+CD4+, CD3+CD8+ and CD20+ cells isolated from patients with ERA, RA and OA exhibited activation of multiple phospho-epitopes. ERA patient PBMCs showed a bias towards phosphorylation-activation in the CD4+ and CD20+ compartments compared to OA PBMCs, where phospho-activation was primarily observed in CD8+ cells. The ratio of phospho (p)-AKT/p-p38 was significantly elevated in patients with ERA and may have diagnostic potential. The mean fluorescent intensity (MFI) levels for p-AKT and p-H3 in CD4+, CD8+ and CD20+ T cells correlated directly with physician global assessment scores (MDGA) and DAS (disease activity score). Stratification by medications revealed that patients receiving leflunomide, systemic steroids or anti-TNF therapy had significant reductions in phospho-specific activation compared with patients not receiving these therapies. Correlative trends between medication-associated reductions in the levels of phosphorylation of specific signaling effectors and lower disease activity were observed. Conclusions Phospho-flow analysis identified phosphorylation-activation of specific signaling effectors in the PB from patients with ERA. Notably, phosphorylation of these signaling effectors did not distinguish ERA from late RA, suggesting that the activation status of discrete cell populations is already established early in disease. However, when the ratio of MFI values for p-AKT and p-p38 is >1.5, there is a high likelihood of having a diagnosis of RA. Our results suggest that longitudinal sampling of patients undergoing therapy may result in phospho-signatures that are predictive of drug responsiveness.

The role of circulating fibrocytes in inflammation and autoimmunity.

Autoimmunity is a chronic process resulting in inflammation, tissue damage, and subsequent tissue remodeling. Circulating fibrocytes are bone marrow‐derived cells with characteristics of hematopoietic and mesenchymal cells. These cells have been implicated in many inflammatory and fibrotic conditions as well as in wound healing. Fibrocytes can amplify the inflammatory/immune response through multiple mechanisms, including antigen presentation, cytokine and chemokine secretion, and production of MMPs. Increased numbers of circulating fibrocytes are observed in RA, systemic scleroderma, and Gravesˈ disease. Here, we review the current literature and potential involvement of fibrocytes in inflammation and autoimmunity.

Circulating fibrocytes contribute to the pathogenesis of collagen antibody–induced arthritis

OBJECTIVE Rheumatoid arthritis (RA) is a systemic autoimmune disease resulting in joint inflammation. Fibroblast-like synoviocytes in affected joints are responsible for pannus formation and cytokine/chemokine production, resulting in leukocyte recruitment and bone/cartilage destruction. Previously, we identified a multipotent stem cell population of activated fibrocytes in the blood of patients with RA that may have a role in disease pathogenesis, perhaps as fibroblast-like synoviocyte precursors. The aim of this study was to further characterize the contribution of circulating fibrocytes to the pathogenesis of RA. METHODS Circulating fibrocytes were isolated from mice with collagen-induced arthritis and transferred intravenously into recipient mice with collagen antibody-induced arthritis (CAIA). The activation status of circulating fibrocytes was determined using multidimensional phosphoflow cytometric analysis of the signaling effectors STAT-5, STAT-1, AKT, and JNK. Circulating fibrocyte trafficking and matrix metalloproteinase (MMP) activity were assessed in real time using fluorescence molecular tomography, specifically labeling circulating fibrocytes with CellVue Maroon and measuring MMP activity using MMPSense 680. RESULTS The numbers of circulating fibrocytes were increased early during the onset of CAIA, concomitant with their activation, as measured by phosphorylation of STAT-5. Adoptive transfer of circulating fibrocytes augmented disease scores and increased class II major histocompatibility complex expression and peripheral blood phosphoactivation profiles in recipient mice with CAIA. Notably, adoptively transferred fluorescence-labeled circulating fibrocytes rapidly migrated into the affected joints of recipient mice with CAIA, and this was associated with augmented neutrophil recruitment into affected joints and MMP activation. CONCLUSION Circulating fibrocytes migrate to joints and influence the onset of disease processes in arthritis.