Antigen-specific plaque-forming cell response of human cord blood lymphocytes after in vitro stimulation by T cell-dependent antigens

Umbilical cord blood and peripheral blood-derived regulatory T cells therapy: Progress in type 1 diabetes

Regulatory T cells (Tregs) are key regulators for the inflammatory response and play a role in maintaining the immune tolerance. Type 1 diabetes (T1D) is a relatively common autoimmune disease that results from the loss of immune tolerance to β-cell-associated antigens. Preclinical models have demonstrated the safety and efficacy of Tregs given in transplant rejection and autoimmune diseases such as T1D. Adoptive transfer of Tregs has been utilized in clinical trials for over a decade. However, the achievement of the adoptive transfer of Tregs therapy in clinical application remains challenging. In this review, we highlight the characterization of Tregs and compare the differences between umbilical cord blood and adult peripheral blood-derived Tregs. Additionally, we summarize conditional modifications in the expansion of Tregs in clinical trials, especially for the treatment of T1D. Finally, we discuss the existing technical challenges for Tregs in clinical trials for the treatment of T1D.

Characterization of early activation events in cord blood B cells after stimulation with T cell-independent activators

Human neonates are immunologically immature, particularly in their humoral antibody responses to T cell-independent antigens, as exemplified by their increased susceptibility to infections with polysaccharide-encapsulated bacteria. To clarify the mechanism(s) underlying the unresponsiveness of neonates to polysaccharide antigens, we used an in vitro model with neonatal cord blood cells that has been shown to mimic surface Ig-dependent signaling in the adult by T cell-independent antigens. We studied the ability of cord blood human B cells to become activated after ligation of their surface Ig by unconjugated anti-Ig, dextran-conjugated anti-Ig, and Staphylococcus aureus Cowan A1, and compared their response with that of adult B cells. After the addition of nanogram concentrations of anti-Ig-dextran, neonatal cord blood B cells proliferated at levels comparable to that observed with adult B cells. The majority of cord blood B cells showed a marked rise in intracellular calcium, increased surface expression of human leukocyte antigen DR, and an increase in cell size. Direct activation of protein kinase C by phorbol esters in neonatal B cells led to cellular proliferation, and when combined with anti-Ig, a synergistic effect on proliferation was observed. These data suggest that the unresponsiveness of human neonates to polysaccharide antigens does not represent an inability of these antigens to induce early activation events in circulating B cells.

Neonatal interleukin-1 beta, interleukin-6, and tumor necrosis factor: cord blood levels and cellular production

In a prospective study, levels of interleukin-1 beta (IL-1 beta), interleukin-6) (IL-6), and tumor necrosis factor (TNF) were measured in a blind fashion in cord blood plasma from 92 neonates by specific immunoassays, and were correlated with the clinical courses of the infants, including type of delivery and perinatal complications. Plasma IL-1 beta concentration was undetectable in infants born by normal vaginal delivery or elective cesarean section but was significantly increased in infants born after induced vaginal deliveries (142 +/- 68 pg/ml) or urgent cesarean section (290 +/- 21 pg/ml; both p less than 0.05 compared with normal deliveries). The IL-1 beta levels were elevated in infants with severe perinatal complications (282 +/- 116 pg/ml; p less than 0.001), whereas TNF and IL-6 levels were not related to these complications. Infants with isolated perinatal infectious complications had elevated levels of plasma IL-6 compared with those of sick neonates without infection (p less than 0.001). In contrast, TNF plasma levels and IL-1 beta production by cord blood leukocytes were decreased in infants with infectious complications alone (both p less than 0.05). These studies suggest that the levels of IL-1 beta, IL-6, and TNF in the cord plasma relate differentially to clinical complications in the perinatal period.

Experimental studies of immunologically mediated enteropathy. VI. Inhibition of acute intestinal graft-versus-host reaction in mice by 2'-deoxyguanosine

We have attempted to investigate the relative roles of specific cytotoxic T lymphocytes (CTL) and allospecific suppressor T cells (Ts) in the systemic and intestinal manifestations of acute graft-versus-host reaction (GvHR) in mice. Treatment of adult (C57B1/10 x DBA/2)F1 (BDF1) mice with the suppressor cell-specific toxin 2'-deoxyguanosine (dGuo) inhibited the weight loss and mortality which normally occur after induction of GvHR and C57Bl donor cells. dGuo also delayed the development of a destructive enteropathy as typified by jejunal villus atrophy. Paradoxically, dGuo completely prevented villus atrophy during an acute GvHR in neonatal (CBA x BALB/c)F1 hosts, despite having only a slight ability to inhibit the systemic disease. In both models, dGuo had no effect on the generation of splenomegaly or anti-host CTL, and dGuo-treated mice with GvHR actually had increased proliferative alterations in the intestine, as assessed by crypt hyperplasia. In parallel, dGuo prevented the loss of NK cells which normally occurs in acute GvHR. Thus dGuo inhibits many of the destructive features of systemic and intestinal GvHR without affecting the development of CTL. We conclude that a dGuo-sensitive mechanism causes the transition from a proliferative to a destructive GvHR.

Interleukin 1 in the in vitro antigen-induced antibody response in the human adult and newborn

Previous studies have shown that in vitro stimulation of human B lymphocytes with antigens such as ovalbumin (OA) induces the formation of small antigen-specific plaque-forming cells (PFC) but precludes the activation of the B cells into full-blown antibody-secreting cells. Insufficient production of T cell-derived growth and differentiation factors appears to be the basis of the phenomenon. Furthermore, cord blood B lymphocytes required 100 times less OA to become activated in vitro into antigen-specific PFC, and the distinct antigen-handling capacities of neonatal monocytes are the basis of this result. We have studied the role of interleukin 1 (IL-1) in the in vitro response of B lymphocytes from either cord blood or adult blood to OA. Addition of IL-1 to the B-cell cultures significantly increased the number of PFC, and about 50% of the plaques now appeared to be high-rate IgM anti-OA-secreting PFC. The IL-1-mediated increase in the PFC response was shown to be based on potentiation of T-helper cell activity. The differences between cord blood and adult blood mononuclear cells in the optimal OA concentration required for effective in vitro activation of B cells remained the same upon addition of IL-1. This result shows that the phenomenon is independent of IL-1.

Heterogeneity of immune defects in three children with a chronic active Epstein-Barr virus infection

Three children, all girls, showed long-lasting clinical and serologic evidence of chronic active Epstein-Barr virus (EBV) infection. Extremely high serum titers of IgG- and IgA-type VCA antibodies and EA antibodies were present, whereas EBNA antibody titers were in the range of those found in seropositive individuals. All three patients repeatedly showed the presence of nonspecific pokeweed mitogen (PWM)-activatable suppressor cells in the peripheral blood. The analysis of EBV-specific cytotoxic T cells showed that one patient exhibited normal cytotoxicity, whereas a second patient demonstrated no EBV-specific cytotoxicity together with unusually high levels of virus-infected B cells in the blood and lymph node. The third patient repeatedly showed refractoriness of the circulating B cells to EBV infection, probably on the basis of some developmental defect. It was concluded that each patient has his or her own peculiar defect in the virus-host balance, indicating that heterogeneity may underlie the syndrome of chronic active EBV infection in humans.

Human T-lymphocyte response in vitro to synthetic peptides of herpes simplex virus glycoprotein D

Immunization of mice with a synthetic peptide that corresponds to a murine antibody-defined immunodominant domain of herpes simplex virus (HSV) glycoprotein D (gD) induced neutralizing antibodies against HSV types 1 and 2 and protected animals against a lethal challenge with HSV type 2 (Dietzschold, B., Eisenberg, R., Ponce de Leon, M., Golub, E., Hudecz, F., Varicchio, A. & Cohen, G. (1984) J. Virol. 52, 431-435). We report here that human peripheral blood T cells from HSV-seropositive and -seronegative adult donors are activated by this synthetic peptide in vitro. Interleukin-2-dependent T-cell lines established from these cultures respond specifically to peptides containing residues 1-23 of HSV gD and to a panel of overlapping peptides within this domain. The T-cell proliferative response was maximal when the majority of interleukin-2-propagated T cells were of the helper phenotype and the peptides were at least 16 amino acids long. Peptides of 8 or 12 amino acids from the carboxyl terminus were nonstimulatory. Peptide-activated T-cell lines from sero-negative donors less than 11 years old could be established in vitro, but most cells were of the suppressor/cytotoxic phenotype and demonstrated no antigen-specificity when tested with the panel of synthetic peptides.

Antigen-induced plaque-forming cell responses in cultures of peripheral blood mononuclear cells of human neonates and infants

Human cord blood mononuclear cells (CBMC) were stimulated in vitro with a number of T cell-dependent antigens. Antigen-induced B cell activation was measured applying a plaque-forming cell assay for the detection of antigen-specific IgM-secreting B cells. With the exception of diphtheria toxoid, the antigens ovalbumin, sheep red blood cells, Helix pomatia hemocyanin, burro red blood cells, and tetanus toxoid elicited an IgM-plaque-forming cell response in cultures of CBMC to levels obtained for peripheral blood mononuclear cells (PBMC) from adult controls. However, for each antigen used, the antigen dose optimal for the induction of a response was consistently found to be a hundred to a thousand times lower than the concentration of the corresponding antigen optimal for adult PBMC. Longitudinal studies on PBMC obtained from infants between 2 and 30 months of age revealed that a shift of the antigen dose toward concentrations needed to induce plaque-forming cells in cultures of adult PBMC occurs at approximately age 8 months. Our data indicate that various antigens can be used for the in vitro analysis of antigen-specific B cell activation and regulatory T cell functions in studies concerning the ontogeny of the humoral immune response in humans.