Adventitial matrix metalloproteinase production and distribution of immunoglobulin G4-related abdominal aortic aneurysms

Immunoglobulin G4-related solitary aneurysm of the deep femoral artery

We have reported the case of an 83-year-old man with a rare immunoglobulin G4 (IgG4)-related solitary deep femoral artery aneurysm. The patient successfully underwent aneurysmectomy and vascular reconstruction with an expanded polytetrafluoroethylene graft. A definitive diagnosis was determined from the comprehensive diagnostic criteria, including histopathologic features of chronic inflammation indicated by massive infiltration of IgG4-positive plasma cells. IgG4-related aneurysmal diseases should be included in the differential diagnosis of deep femoral artery aneurysms, which have traditionally been considered to develop owing to previous trauma or surgery, intervention, infection, and autoimmune or collagen disease.

The disturbance of the distribution of T helper cell subsets in the mantle area surrounding germinal centers in immunoglobulin G4-related sclerosing sialadenitis

The function of germinal centers (GCs) is an important factor in the pathogenesis of immunoglobulin G4 (IgG4)-related disease, in which inflammatory and fibrotic processes are controlled by type 2 helper T (Th) cells and regulatory T cells. T follicular helper cells (Tfh), which are present in GCs, regulate GC development, and they consist of Tfh1, Tfh2, and Tfh17 subsets. This study examined the association of Th cell subsets in IgG4-RD and pathogenesis of the disease using whole-slide image analysis for immunohistochemistry. IgG4-related sclerosing sialadenitis (IgG4-SS, n = 19) was characterized by higher numbers of Tfh2 and Tfh17 cells than Tfh1 cells compared to the findings in patients with chronic sialadenitis (n = 18) or Sjögren syndrome (n = 17). The number of Tfh2 cells was significantly associated with all parameters of GC structures and the number of IgG4 + plasmacytes, whereas the number of Tfh1 cells was inversely associated with the aforementioned parameters. Concerning extrafollicular helper T (Teh) cells, among three groups, the Tfh2/Teh2 ratio was highest and the Tfh1/Teh1 ratio was lowest in the IgG4-SS group, which exhibited a characteristically regional distribution of Tfh and Teh subsets, especially higher numbers of Teh2 cells and lower numbers of Teh1 cells in the mantle areas surrounding GCs. Mantle Teh2 cells and central Tfh17 cells were significantly correlated with morphological abnormalities of GCs. Our results indicated that the peculiar regional distribution and altered balance of Tfh and Teh subsets are novel hallmarks of IgG4-SS that are associated with GC formation in IgG4-SS.

Regional disturbance of the distribution of T regulatory cells and T helper cells associated with irregular-shaped germinal centers in immunoglobulin G4-related sialadenitis

Although many germinal centers (GCs) have been reported in immunoglobulin (Ig) G4-related disease, the significance of GCs in IgG4-related disease has not received attention. Both T follicular regulatory cells (Tfr), which are regulatory T cells (Treg) in GCs, and T follicular helper cells (Tfh) produce the cytokine interleukin (IL)-10 and regulate GC development. In whole-slide image analysis in surgical specimens using immunohistochemistry, IgG4-related sclerosing sialadenitis (IgG4-SS, n = 17) was characterized by markedly numerous, large, and irregular-shaped GCs with increased IL-10 + cells and Tfr and Tfh in the total area of the salivary gland compared with controls, including patients with chronic sialadenitis (n = 17) and Sjögren syndrome (n = 15). In particular, the central area of GC in IgG4-SS showed a higher Tfr number and Tfr/Tfh ratio than controls. The number of Tfr in the central area was significantly correlated with the number of IgG4 + plasmacytes and the number, size, and irregularity of GCs. In the mantle area, which surrounds GCs, IgG4-SS showed a higher Treg number and Treg/T helper cells (Th) ratio than controls. In IgG4-SS, the Treg/Th ratio was highest in the mantle area outside GCs and the Tfr/Tfh ratio was highest in the central area inside GCs. However, in controls, the Treg/Th ratio gradually decreased from outside to inside GCs. Our findings reveal that the morphological abnormality of GCs and the characteristic localization and altered balance of Treg and Th in the different compartments of inside and outside GCs would be the novel hallmarks of IgG4-SS.