Impaired CD8(+) T cell responses upon Toll-like receptor activation in common variable immunodeficiency.

BACKGROUND: Infections caused by bacteria or viruses are frequent in common variable immunodeficiency (CVID) patients due to antibody deficiencies, which may be associated with altered T cell function. CVID patients are frequently in contact with pathogen-associated molecular patterns (PAMPs), leading to the activation of innate immunity through Toll-like receptors (TLR) affecting T cell activation. We evaluated the effect of TLR activation on T cells in CVID patients undergoing intravenous immunoglobulin (IVIg) replacement using synthetic ligands. METHODS: Expression of exhaustion, activation and maturation markers on T cells from peripheral blood as well as regulatory T cells and follicular T cells in peripheral blood mononuclear cells (PBMCs) from CVID and healthy individuals were evaluated by flow cytometry. PBMCs cultured with TLR agonists were assessed for intracellular IFN-γ, TNF, IL-10, IL-17a or IL-22 secretion as monofunctional or polyfunctional T cells (simultaneous cytokine secretion) by flow cytometry. RESULTS: We found increased expression of the exhaustion marker PD-1 on effector memory CD4(+) T cells (CD45RA(-)CCR7(-)) in the peripheral blood and increased expression of CD38 in terminally differentiated CD8(+) T cells (CD45RA(+)CCR7(-)). Furthermore, a decreased frequency of naïve regulatory T cells (CD45RA(+)Foxp3(low)), but not of activated regulatory T cells (CD45RA(-)Foxp3(high)) was detected in CVID patients with splenomegaly, the non-infectious manifestation in this CVID cohort (43.7 %). Moreover, the frequency of peripheral blood follicular helper T cells (CD3(+)CD4(+)CXCR5(+)PD-1(+)ICOS(+)) was similar between the CVID and control groups. Upon in vitro TLR3 activation, a decreased frequency of CD8(+) T cells secreting IFN-γ, IL-17a or IL-22 was detected in the CVID group compared to the control group. However, a TLR7/TLR8 agonist and staphylococcal enterotoxin B induced an increased Th22/Tc22 (IL-22(+), IFN-γ(-), IL-17a(-)) response in CVID patients. Both TLR2 and TLR7/8/CL097 activation induced an increased response of CD4(+) T cells secreting three cytokines (IL-17a, IL-22 and TNF)in CVID patients, whereas CD8(+) T cells were unresponsive to these stimuli. CONCLUSION: The data show that despite the unresponsive profile of CD8(+) T cells to TLR activation, CD4(+) T cells and Tc22/Th22 cells are responsive, suggesting that activation of innate immunity by TLRs could be a strategy to stimulate CD4(+) T cells in CVID.

Evidence of regulatory myeloid dendritic cells and circulating inflammatory epidermal dendritic cells-like modulated by Toll-like receptors 2 and 7/8 in adults with atopic dermatitis.

BACKGROUD: Atopic dermatitis (AD) is a chronic, inflammatory skin disease characterized by intense pruritus and xerosis. Dendritic cells (DC) play an essential role in tissue inflammation in atopic dermatitis (AD) skin, especially the inflammatory epidermal dendritic cells (IDEC), a particular subset of myeloid dendritic cells (mDC). The aim of the present study was to assess the phenotype and function of mDC and circulating IDEC-like in peripheral blood mononuclear cells (PBMC) of adults with AD. METHODS: We selected 21 AD patients and 21 non-AD controls, age and gender matched. Expressions of FcεRI, CD36, TNF, IFN- γ, and IL-10 in mDC were analyzed by flow cytometry under various stimuli, such as staphylococcal enterotoxin B (SEB), TLR2 (Pam3CSK4), TLR4 (LPS), and TLR7/8 (CL097) agonists. RESULTS: The most prominent findings in AD patients were: (i) enhanced frequency of IL-10 under TLR4 (LPS), and decreased frequency of IFN-γ and TNF under TLR2 (Pam3CSK4) and 7/8 (CL097) stimulation in classic mDC; (ii) elevation of circulating IDEC-like frequency with TLR2 (Pam3CSK4) stimuli, augmented frequency of IFN-γ in nonstimulated condition, and of IL-10 under TLR7/8 (CL097) stimuli in IDEC-like population. CONCLUSIONS: In AD individuals, classic mDC showed an immunomodulatory profile, favoring tolerance in a combined action with IDEC-like, and inducing Th1 polarization. Our findings indicate a potential role of IDEC-like in the maintenance of inflammation in atopic dermatitis patients; moreover, IDEC-like may exert a regulatory impact on T cells of AD individuals through IL-10, often induced by agonist mimicking single stranded RNA virus.