Human colonic intraepithelial lymphocytes regulate the cytokines produced by lamina propria mononuclear cells

Using an in vitro autologous human system, the immunomodulatory function of colonic intraepithelial lymphocytes (IEL) on cytokine production by lamina propria mononuclear cells (LPMNC) has been investigated. In contrast to LPMNC, colonic IEL produced only low amounts of IL-10, interferon-γ and interleukin-2. However, co-culture experiments (IEL + LPMNC) have shown that IEL can enhance the PHA-induced synthesis of IL-2 and interferon-γ, but not IL-10 by LPMNC. Using a transwell filter culture system apparatus, this effect was shown not to require a cell-to-cell interaction. Thus, IEL in vitro may modulate the cytokine synthesis of LPMNC, through the production of soluble factors. This may prove highly relevant in the in vivo immune activation of the gastrointestinal mucosa

Secretion of immunoglobulins and plasma proteins from the colonic mucosa: an in vivo study in man.

There are no available data on immunoglobulins and albumin outputs into the normal human colon. We thus measured the intracolonic secretion rates of IgA, IgG, IgM, secretory component (SC) and plasma proteins (albumin (Alb), orosomucoid (Oro), transferrin (Transf) and alpha 2-macroglobulin (alpha 2-M)). Using a pancolonic perfusion technique in 10 healthy volunteers (six females, four males, mean age 24 years), concentrations and outputs of Alb, immunoglobulins, SC, Oro, Transf and alpha 2-M were measured in the rectal effluents by immunoradiometric assay. Monomeric (m) and polymeric (p) IgA distribution was analysed by sucrose density ultracentrifugation. The secretion of polymeric IgA (p-IgA) was 153 micrograms/min, i.e. 220 mg/day, exceeding that of other immunoglobulins (m-IgA 8.5 micrograms/min; IgG 33.5 micrograms/min; IgM 17 micrograms/min) and of non-immunoglobulin proteins (Alb 104 micrograms/min; Oro 9 micrograms/min; Transf 7 micrograms/min; alpha 2-M 4.5 micrograms/min). p-IgA was entirely linked to SC (secretory IgA) and 12% of SC was in free form. About 62% of total IgA was IgA2. For each protein, a relative coefficient of excretion (RCE) was calculated (colon to serum concentration ratio expressed relative to that of Alb). The p-IgA, IgM and m-IgA RCE were 277, 6 and 2.2 times higher than the values predicted from their molecular weight. RCE of non-immunoglobulin proteins also exceeded the values expected from a passive seepage from the vascular compartment. The intracolonic clearance of Alb extrapolated to 24 h was only 3.7 ml/day. These results show the high local production and/or the facilitated transport to the colonic lumen of p-IgA, and are in very good agreement with the distribution of plasma cells in the colonic mucosa

Effect of intrajejunal elemental diet perfusion on jejunal secretion of immunoglobulins, albumin, and hyaluronan in man.

The aim of this work was to study the jejunal secretion of immunoglobulins (Ig), albumin, and hyaluronan in response to jejunal perfusion of an elemental diet. A four lumen tube with a proximal occluding balloon at the angle of Treitz was used for jejunal perfusion in seven healthy volunteers (mean age 23 years). The length of the test segment was 40 cm. The jejunum was successively perfused with a control electrolyte solution for 80 minutes and with an elemental diet (containing 20.5 milligrams of free amino acids and 104.2 milligrams of oligosaccharides) for 100 minutes. The jejunal fluid concentrations of albumin, IgG, monomeric IgA (m-IgA), polymeric IgA (p-IgA), IgM, secretory component, and hyaluronan were measured and their jejunal outputs calculated. Within 20 minutes of starting perfusion with the elemental diet there was a significant increase in the secretion rates of albumin (x3.3), IgG (x5), M-IgA (x3.7), p-IgA (x2), IgM (x2), and secretory component (x1.6), but the hyaluronan secretion rate was not changed. The increase in m-IgA, p-IgA, IgM, and secretory component output suggests that intestinal perfusion of an elemental diet results in stimulation of secretory immunity. The increase in albumin and IgG output probably reflects a nutrient induced leakage from the plasma compartment

Long‐term stability study and evaluation of intact steroid conjugate ratios after the administration of endogenous steroids

The most frequently detected substances prohibited by the World Anti-Doping Agency (WADA) belong to the anabolic steroids class. The most challenging compounds among this class are the endogenous anabolic steroids, which are detected by quantitative measurement of testosterone (T) and its metabolites with a so-called "steroid profiling" method. The current steroid profile is based on the concentrations and ratios of the sum of free and glucuronidated steroids. Recently, our group developed a steroid profiling method for the detection of three free steroids and 14 intact steroid conjugates, including both the glucuronic acid conjugated and sulfated fraction. The study aimed at evaluating the long-term stability of steroid conjugate concentrations and ratios, and the influence of different endogenous steroids on this extended steroid profile. A single dose of oral T undecanoate (TU), topical T gel, topical dihydrotestosterone (DHT) gel, and oral dehydroepiandrosterone (DHEA) was administered to six healthy male volunteers. One additional volunteer with a homozygote deletion of the UGT2B17 gene (del/del genotype) received a single topical dose of T gel. An intramuscular dose of TU was administered to another volunteer. To avoid fluctuation of steroid concentrations caused by variations in urinary flow rates, steroid ratios were calculated and evaluated as possible biomarkers for the detection of endogenous steroid abuse with low doses. Overall, sulfates do not have substantial additional value in prolonging detection times for the investigated endogenous steroids and administration doses. The already monitored glucuronides were overall the best markers and were sufficient to detect the administered steroids