Purification of T cell subpopulations.

This unit describes a procedure for isolating T cell populations or subpopulations using the method of indirect panning. In this method, cells are selected by their capacity to bind to antibody-coated plates on the basis of particular cell-surface markers. It is superior to the antibody/complement lysis method (also presented) because the nonselected cell population can be retrieved.

Reduced numbers of CD8+ T cells and B cell-expression of Leu-8 antigen in peripheral blood of patients with primary biliary cirrhosis.

The presence of Leu-8 antigen, the human homologue of the murine MEL-14 peripheral lymph node homing receptor, defines subsets of peripheral blood mononuclear cells (PBMC) with different functions. Since it has been suggested that abnormal function of Leu-8 subsets may contribute to the immunopathogenesis of primary biliary cirrhosis (PBC), this study was undertaken to define whether abnormal expression of the Leu-8 antigen occurs in this disease. We studied 25 PBC patients, 12 with other chronic liver diseases, and 21 normal controls. PBMC were tested by direct immunofluorescence using monoclonal antibodies and flow cytometry. In PBC the proportion of PBMC that were CD4+ was normal; in contrast, the proportion that were CD8+ was decreased (p < 0.01). A negative correlation was found between absolute numbers of CD8+ T cells and total serum bilirubin levels (r = -0.50, p < 0.05). The distribution of Leu-8 antigen on T cells was normal; however, the proportion of PBMC that were B cells was increased (p < 0.01) and the fraction of these that were Leu-8 negative was also increased (p < 0.01). The expression of antigens of activation on B cells was similar to that for normal controls. These findings suggest that in peripheral blood of PBC patients reduced numbers of T cells may occur due to a selective intrahepatic sequestration of CD8+ T cells, and that the decreased expression of Leu-8 antigen by B cells may be associated with their participation in autoimmune processes.

Defective proliferation and regulatory function of CD4+ T cells bearing Leu-8 homing receptor in primary biliary cirrhosis. Phorbol myristate acetate enhances T-cell function.

The majority of circulating CD4+ T cells express the Leu-8 peripheral lymph node homing receptor, and these cells have previously been shown to have suppressor-inducer and suppressor function. In the present study, it was found that CD4+, Leu-8+ T cells from patients with primary biliary cirrhosis (PBC) have a significantly (P < 0.01) lower proliferative response when stimulated with phytohemagglutinin (PHA), concanavalin A (Con A), or pokeweed mitogen (PWM) compared to normal controls. The proliferative response of CD4+, Leu-8- T cells was similar in patients and controls. However, the proliferative responses of CD4+, Leu-8+ from patients with PBC was normal when cells were stimulated with PHA, Con A, anti-CD3 monoclonal antibody, or ionomycin in combination with phorbol myristate acetate (PMA). CD4+ T cells from patients with PBC mediated normal helper function for PWM-stimulated immunoglobulin synthesis at high T/B ratios and their regulatory function was similar to that of normal CD4+ T cells that had been irradiated to inactivate their suppressor activity. When CD4+ T cells from patients with PBC were precultured with the combination of Con A and PMA, they mediated potent inhibitory activity similar to that of normal CD4+ T cells. Thus, CD4+, Leu-8+ T cells from patients with PBC have a defect of proliferation and suppressor function that is reversed by coculture with PMA. This finding suggests that impairment of a PMA-inducible lymphocyte activation pathway contributes to abnormal lymphocyte function in PBC.

CD4+ Leu-8+ T cell supernatant activity that inhibits Ig production.

The subpopulation of CD4+ T cells that expresses the Leu-8 peripheral lymph node homing receptor suppresses PWM-stimulated Ig synthesis. To determine the mechanism of this suppression, the immunoregulatory activity of culture supernatants obtained from peripheral blood CD4+ Leu-8+ T cells cultured with anti-CD3 mAb and PMA (Leu-8+ supernatant) was determined. Leu-8+ supernatant suppressed PWM-stimulated Ig synthesis in cultures containing non-T cells and CD4+ Leu-8- T cells. In contrast, the supernatant from CD4+ Leu-8- T cells did not suppress Ig synthesis. The inhibitory activity of CD4+ Leu-8+ T cell supernatants could not be accounted for by a deficiency or excess of IL-2, IL-4, IFN-gamma, IL-6, or PGE2. In studies examining the effect of CD4+ Leu-8+ supernatant on T cells, the supernatant did not alter either mitogen-induced proliferation or the helper function of CD4+ Leu-8- T cells. In studies examining the effect of CD4+ Leu-8+ supernatant on B cells, the supernatant inhibited Staphylococcus aureus Cowan I strain-induced B cell Ig secretion but not B cell proliferation. The suppressor activity of Leu-8+ supernatant was eliminated by protease treatment and was eluted by HPLC in two main peaks, with molecular sizes of 44 and 12 kDa. In summary, these studies indicate that supernatants from activated CD4+ Leu-8+ T cells directly suppress B cell Ig production.

Role of lymphokines in immunoregulatory function of mucosal T cells in humans and nonhuman primates.

The findings presented above and in other studies provide substantial evidence that lymphocytes in the intestinal lamina propria differ from lymphocyte populations in the circulation or in other tissue sites in a number of ways. First, lamina propria lymphocytes are phenotypically distinct and have evidence of activation. Lymphocytes in the intestinal lamina propria are different in their potential for expression of lymphokine gene products, since activated cells from the lamina propria have high expression of mRNA for IL-2, IL-4, IL-5 and IFN-gamma in comparison to circulating lymphocytes. Mesenteric lymph node T cells also differ from circulating lymphocytes in their high expression of IL-4 and IL-5 mRNA. A further difference between mesenteric lymph node and lamina propria T cells is that the former are capable of proliferating in response to IL-4, whereas the latter are not. These phenotypic and mRNA differences of lamina propria lymphocytes also correlate well with their high helper activity in vitro for immunoglobulin synthesis in the pokeweed mitogen system. Finally, lamina propria T cells at a site of inflammation are able to provide high helper activity in response to specific antigens. These observations are all consistent with the conclusion that T cells in the lamina propria are pleomorphic, but are highly enriched for subpopulations of activated memory cells that are geared for effector functions. These functions are likely to be critical in maintaining normal host defense in the mucosal environment.

Multiple roles of Leu-8/MEL-14 in leukocyte adhesion and function.

Leu-8 and its murine homologue MEL-14 are members of a new family of adhesion molecules encoded on chromosome-1 that share common structural features, including lectin-like domains and tandem repeats homologous to complement binding proteins. The expression of Leu-8 is rapidly down-regulated during cell activation, both at the transcriptional level, and by a rapid post-translational event at the cell membrane, probably involving direct cleavage of the molecule from the cell surface. Lymphocytes that express Leu-8/MEL-14 bind selectively to HEVs in peripheral lymph nodes, and MEL-14 on neutrophils is thought to be important in the initial localization of neutrophils to sites of inflammation. In addition to its role in leukocyte adhesion, there is evidence that the Leu-8 molecule plays a role in cell function. Anti-Leu-8 monoclonal antibody increases suppressor activity of CD4+, Leu-8+ T cells for immunoglobulin synthesis, and anti-Leu-8 directly inhibits differentiation of Leu-8+ B cells. Together these findings indicate that the Leu-8 molecule in common with other cellular adhesion molecules is important not only in cellular adhesion, but also in modification of cell function.

Defective immunoregulation in primary biliary cirrhosis: CD4+, Leu-8+ T cells have abnormal activation and suppressor function in vitro.

To determine whether abnormalities of lymphocyte function in primary biliary cirrhosis are due to altered function of immunoregulatory T cell subpopulations, phenotypic and functional characteristics of CD4+ T cells were examined. The proportion of CD4+ T cells expressing the Leu-8 and CD45R antigens was normal in patients with primary biliary cirrhosis. The capacity of CD4+, Leu-8- T cells to provide helper function for pokeweed mitogen-stimulated immunoglobulin synthesis by B cells in vitro was similar in patients and controls. However, in contrast to normal individuals and patients with other liver diseases, CD4+, Leu-8+ T cells from six of 10 patients with primary biliary cirrhosis did not suppress, but enhanced immunoglobulin synthesis. Whereas treatment of CD4+ T cells from normal individuals with anti-Leu-8 monoclonal antibody enhanced their suppressor function, similar treatment of CD4+ T cells from patients with primary biliary cirrhosis did not increase their suppressor function. To determine whether the abnormal regulatory function of CD4+, Leu-8+ T cells was due to a defect of cell activation, the proliferative response of CD4+ T cell subpopulations to mitogenic stimulation was examined. The proliferative responses of CD4+, Leu-8- T cells from patients with primary biliary cirrhosis and controls were similar, but the proliferative responses of CD4+, Leu-8+ T cells from patients with primary biliary cirrhosis were lower than those of control cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased height velocity in children and adolescents before the diagnosis of Crohn's disease.

Severe linear growth retardation occurs in 20%-30% of children with Crohn's disease, yet, it is unknown how often decreased height velocity precedes the diagnosis. The height velocities of 50 children and prepubescent adolescents with Crohn's disease were reviewed. Decreased height velocity antedated the diagnosis in 44 patients. Twenty-one patients had a reduction in height velocity before intestinal symptoms were noted. Additionally, 17 of 32 patients with attenuated linear growth had a reduction in height velocity before any weight loss. Linear growth impairment in Crohn's disease, more common than previously recognized, may precede weight loss and can be the earliest indicator of disease.

CD4 positive Leu-8 negative helper-inducer T cells predominate in the human intestinal lamina propria.

The regulatory function of peripheral blood CD4 T cells correlates with the presence or absence of the membrane glycoprotein recognized by anti-Leu-8 antibody; CD4,Leu8- T cells help Ig synthesis and CD4,Leu-8+ T cells suppress Ig synthesis. In contrast to CD4 T cells from the peripheral blood and organized gut-associated lymphoid tissues, intestinal lamina propria CD4 T cells were found to have diminished expression of the Leu-8 Ag. Therefore, studies were performed to determine whether the decreased expression of the Leu-8 Ag on lamina propria CD4 T cells correlates with a difference in the ability of peripheral blood and lamina propria CD4 T cells to regulate PWM-stimulated Ig synthesis. At high T cell to non-T cell ratios, the helper function of lamina propria CD4 T cells was significantly higher than that of peripheral blood CD4 T cells. When CD4 T cells were incubated with anti-Leu-8 antibody, the suppressor function of peripheral blood CD4 T cells was increased, but lamina propria CD4 T cells did not suppress Ig synthesis. No difference was found between the helper function of CD4,Leu-8- T cells and the suppressor function of CD4, Leu-8+ T cells isolated from either the peripheral blood or the lamina propria. Thus, the difference in the regulatory function of CD4 T cells from the peripheral blood and the lamina propria is due to the quantitative difference in CD4,Leu-8+ T cells in these sites. Consequently, the intestinal lamina propria is a site enriched in CD4,Leu-8- T cells which predominantly mediate help for Ig synthesis.

Leu-8 antigen expression is diminished during cell activation but does not correlate with effector function of activated T lymphocytes.

Previous studies have suggested that there is an inverse relationship between cell activation and the expression of the Leu-8 Ag, a cell surface protein that distinguishes functionally distinct T cell populations. This was confirmed in vitro, because when resting PBL were activated with PHA there was a rapid decline in expression of the Leu-8 Ag on all lymphocyte subpopulations. A decline in Leu-8 reactivity occurred after stimulation of lymphocytes with PHA, anti-CD3 plus PMA and ionomycin plus PMA, and an intermediate decline in Leu-8 expression occurred after stimulation with Con A. However, there was little loss of expression of Leu-8 after stimulation of lymphocytes with PWM or allogeneic lymphocytes. The decline in Leu-8 expression on activated lymphocytes occurred earlier than the decline in expression of CD45R. After removal of the activation stimuli, peripheral blood T cells or Jurkat cells rapidly re-expressed Leu-8. Finally, when the expression of Leu-8 on peripheral blood CD4+, Leu-8+ T cells was reduced by prior activation with PHA, these cells continued to exhibit suppressor function for PWM-stimulated Ig synthesis. Thus, there is a rapid decline in expression of the Leu-8 Ag but no change in regulatory function of CD4+, Leu-8+ T cells during cell activation. These results suggest that the molecule recognized by anti-Leu-8 plays a role in lymphocyte activation but not directly in the effector function of CD4+, Leu8+ T cells.

Induction of CD4 suppressor T cells with anti-Leu-8 antibody.

To characterize the conditions under which CD4 T cells suppress polyclonal immunoglobulin synthesis, we investigated the capacity of CD4 T cells that coexpress the surface antigen recognized by the monoclonal antibody anti-Leu-8 to mediate suppression. In an in vitro system devoid of CD8 T cells, CD4, Leu-8+ T cells suppressed pokeweed mitogen-induced immunoglobulin synthesis. Similarly, suppressor function was induced in unfractionated CD4 T cell populations after incubation with anti-Leu-8 antibody under cross-linking conditions. This induction of suppressor function by anti-Leu-8 antibody was not due to expansion of the CD4, Leu-8+ T cell population because CD4 T cells did not proliferate in response to anti-Leu-8 antibody. However, CD4, Leu-8+ T cell-mediated suppression was radiosensitive. Finally, CD4, Leu-8+ T cells do not inhibit immunoglobulin synthesis when T cell lymphokines were used in place of helper CD4 T cells (CD4, Leu-8- T cells), suggesting that CD4 T cell-mediated suppression occurs at the T cell level. We conclude that CD4 T cells can be induced to suppress immunoglobulin synthesis by modulation of the membrane antigen recognized by anti-Leu-8 antibody.

Pneumatosis intestinalis in children after allogeneic bone marrow transplantation.

Four children, ages 3 to 8 years, developed pneumatosis intestinalis (PI) after allogeneic bone marrow transplantation (BMT) for acute leukemia or severe aplastic anemia. PI was detected at a median of 48 days (range, 10-63 days) after BMT and was associated with abdominal symptoms and clinical signs. All patients had severe systemic and/or high-grade cutaneous acute graft-versus-host disease (AGVHD) at some time after BMT and were receiving corticosteroids at the time of development of PI; however, PI was associated with concomitant severe AGVHD in only one patient. One patient with PI had Hafnia alvei bacteremia and another patient had gastroenteritis due to rotavirus and adenovirus. All patients were treated with supportive care and systemic broad-spectrum antibiotics, and PI resolved 2-16 days after onset. Two patients died with BMT-associated complications unrelated to PI. Multiple factors contribute to the development of PI after BMT, and the prognosis for recovery from PI is good with medical management alone. Overall survival in these patients is dependent on the frequency and severity of other conditions, such as AGVHD and opportunistic infections, after BMT.

Congenital diarrhea with intestinal inflammation and epithelial immaturity.

We report an interesting case of congenital inflammatory bowel disease and intestinal epithelial immaturity that presented as secretory diarrhea. No infectious, metabolic, or anatomical basis for these findings was identified. As differentiated from previous reports of neonatal enteropathies, this infant demonstrated involvement of both the small and large intestine with histopathologic findings of acute and chronic inflammation, extensive submucosal fibrosis, and "flat" small intestine mucosa. In addition, this patient had a polyamine deficiency (a primary or secondary phenomenon), which may have contributed to delayed epithelial maturation. These findings suggest that the inflammatory bowel disease and altered epithelial maturation contributed to a fatal intractable diarrhea.