Upregulation of ICOS on CD43+ CD4+ murine small intestinal intraepithelial lymphocytes during acute reovirus infection

Abstract

Murine intestinal intraepithelial lymphocytes (IELs) can be classified according to expression of a CD43 glycoform recognized by the S7 monoclonal antibody. In this study, we examined the response of S7+ and S7-IELs in mice during acute reovirus serotype 3 (Dearing strain) infection, which was confirmed by virus-specific real-time PCR. In vivo proliferation increased significantly for both S7and S7+ IELs on day 4 post-infection as determined by BrdU incorporation; however, expression of the inducible costimulatory (ICOS) molecule, which peaked on day 7 post-infection, was upregulated on S7+ CD4+ T cells, most of which were CD4+8-IELs. In vitro ICOS stimulation by syngeneic peritoneal macrophages induced IFN-γ secretion from IELs from day 7 infected mice, and was suppressed by treatment with anti-ICOS mAb. Additionally, IFN-γ mRNA increased in CD4+ IELs on day 6 post-infection. These findings indicate that S7-and S7+ IELs are differentially mobilized during the immune response to reovirus infection; that the regulated expression of ICOS is associated with S7+ IELs; and that stimulation of IELs through ICOS enhances IFN-γ synthesis during infection.

The drug monosodium luminol (GVT) preserves crypt-villus epithelial organization and allows survival of intestinal T cells in mice infected with the ts1 retrovirus

“…However, two other differences distinguish the epithelial cells of the intestinal crypts from those of the villi. One is these is the constitutive expression of TSH by crypt epithelial cells, and not by epithelial cells of the villi [37][38][39][40]. The other is the presence of dividing epithelial cells exclusively in crypts, but not in the villi [26].…”

Experimental intestinal reovirus infection of mice

“…Mice were infected with 10 7.5 reovirus type 3 Dearing strain by oral gavage. Previous studies from our laboratory using real-time PCR indicate that virus infection peaked in the small intestine between days 4-7 post infection [68]. On day 4 postinfection, IELs were isolated and cultured overnight in serum-free tissue culture medium.…”

“…Stem cell factor (SCF) would be used in the expansion/development of intestinal T cells during infection [69]. Collectively, the composite effects of those analytes in the host response to enteric virus infection would predictably lead to a strong cell-mediated immune response on day 4 of infection, a time when virus is wide-spread [68].…”

Stimulatory and costimulatory effects of IL-18 directed to different small intestinal CD43 T cell subsets

“…IELs express cytotoxic activity in freshly-isolated preparations [11][12][13][14][15]; however, they normally do not produce cytokines until a stimulatory signal has been received through the TCR/CD3 complex or following mitogen activation [15,16]. Moreover, with the exception of CD69 [15,17], most IELs do not express markers commonly associated with activated T cells, such as OX40, ICOS, or Ly-6C, and when isolated from naïve mice, they are primarily CD44 low and CD45RB high [15]. Following CD3-mediated activation or virus infection, IELs acquire OX40, ICOS, and Ly-6C expression and become CD44 high and CD45RB low [15,17].…”

“…Moreover, with the exception of CD69 [15,17], most IELs do not express markers commonly associated with activated T cells, such as OX40, ICOS, or Ly-6C, and when isolated from naïve mice, they are primarily CD44 low and CD45RB high [15]. Following CD3-mediated activation or virus infection, IELs acquire OX40, ICOS, and Ly-6C expression and become CD44 high and CD45RB low [15,17]. In general, IELs have a low proliferative potential in vitro [18][19][20].…”