Expansion of circulating T cells resembling follicular helper T cells is a fixed phenotype that identifies a subset of severe systemic lupus erythematosus.
OBJECTIVE
In the sanroque mouse model of lupus, pathologic germinal centers (GCs) arise due to increased numbers of follicular helper T (Tfh) cells, resulting in high-affinity anti-double-stranded DNA antibodies that cause end-organ inflammation, such as glomerulonephritis. The purpose of this study was to examine the hypothesis that this pathway could account for a subset of patients with systemic lupus erythematosus (SLE).


METHODS
An expansion of Tfh cells is a causal, and therefore consistent, component of the sanroque mouse phenotype. We validated the enumeration of circulating T cells resembling Tfh cells as a biomarker of this expansion in sanroque mice, and we performed a comprehensive comparison of the surface phenotype of circulating and tonsillar Tfh cells in humans. This circulating biomarker was enumerated in SLE patients (n = 46), Sjögren's syndrome patients (n = 17), and healthy controls (n = 48) and was correlated with disease activity and end-organ involvement.


RESULTS
In sanroque mice, circulating Tfh cells increased in proportion to their GC counterparts, making circulating Tfh cells a feasible human biomarker of this novel mechanism of breakdown in GC tolerance. In a subset of SLE patients (14 of 46), but in none of the controls, the levels of circulating Tfh cells (defined as circulating CXCR5+CD4+ cells with high expression of Tfh-associated molecules, such as inducible T cell costimulator or programmed death 1) were increased. This cellular phenotype did not vary with time, disease activity, or treatment, but it did correlate with the diversity and titers of autoantibodies and with the severity of end-organ involvement.


CONCLUSIONS
These findings in SLE patients are consistent with the autoimmune mechanism in sanroque mice and identify Tfh effector molecules as possible therapeutic targets in a recognizable subset of patients with SLE.
Simpson
Nicholas
N
Australian National University, Canberra, ACT, Australia.
Gatenby
Paul A
PA
Wilson
Anastasia
A
Malik
Shreya
S
Fulcher
David A
DA
Tangye
Stuart G
SG
Manku
Harinder
H
Vyse
Timothy J
TJ
Roncador
Giovanna
G
Huttley
Gavin A
GA
Goodnow
Christopher C
CC
Vinuesa
Carola G
CG
Cook
Matthew C
MC
D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D015703:Antigens, CD / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D015551:Autoimmunity / Q000276:immunology*; D002452:Cell Count; D004195:Disease Models, Animal; D018858:Germinal Center / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology; D060889:Inducible T-Cell Co-Stimulator Protein; D008180:Lupus Erythematosus, Systemic / Q000276:immunology / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D014066:Palatine Tonsil / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D061026:Programmed Cell Death 1 Receptor; D054380:Receptors, CXCR5 / Q000378:metabolism; D012859:Sjogren's Syndrome / Q000097:blood / Q000276:immunology / Q000473:pathology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology / Q000378:metabolism / Q000473:pathology*
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D051017:Apoptosis Regulatory Proteins; C095085:CXCR5 protein, human; C556692:ICOS protein, human; C556694:Icos protein, mouse; D060889:Inducible T-Cell Co-Stimulator Protein; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor; D054380:Receptors, CXCR5