Cutting edge: IL-4 receptor expression by non-bone marrow-derived cells is required to expel gastrointestinal nematode parasites

Expulsion of two gastrointestinal nematode parasites, Nippostrongylus brasiliensis and Trichinella spiralis, is similar in that both require IL-4Ralpha expression, but different in that T cells and mast cells are required for IL-4-induced expulsion of T. spiralis but not N. brasiliensis. To examine the role of IL-4Ralpha signaling in immunity to these parasites, we studied worm expulsion in chimeric mice that selectively expressed IL-4Ralpha on bone marrow-derived or non-bone marrow-derived cells. N. brasiliensis was expelled by mice that expressed IL-4Ralpha only on non-bone marrow-derived cells, but not by mice that expressed IL-4Ralpha only on bone marrow-derived cells. Although T. spiralis expulsion required IL-4Ralpha expression by both bone marrow- and non-bone marrow-derived cells, IL-4 stimulation eliminated the requirement for IL-4Ralpha expression by bone marrow-derived cells. Thus, direct IL-4Ralpha signaling of nonimmune gastrointestinal cells may be generally required to induce worm expulsion, even when mast cell and T cell responses are also required.

[Endoscopic supraglottoplasty in children with severe laryngomalacia with and without neurological impairment]

OBJECTIVE: To describe indications and results of supraglottoplasty for severe laryngomalacia in children with or without neurological impairment. METHODS: Eight children with severe laryngomalacia submitted to endoscopic supraglottoplasty were retrospectively studied. Four had neurological impairment (male, mean age 6 years), and 4 did not present neurological problems (3 female, mean age 11.5 months). Surgery indications were respiratory distress, feeding difficulties, failure to thrive, and low oxygen saturation. Polysomnographic evaluation was carried out on the last 2 children, showing abnormal oxygen saturation, obstructive apnea, and hypoventilation. All children received preoperative antibiotics and corticosteroids. RESULTS: All children without neurological impairment had significant relief of symptoms. Children with neurological impairment had different outcome: one needed tracheotomy immediately after surgery due to edema and supraglottic granulation tissue. The other three children presented initial relief of symptoms, but subsequent follow-up showed progressive airway obstruction: one needed another endoscopic surgery 6 months later; other needed tracheotomy 7 months later. The children who were not submitted to tracheostomy presented persistent severe airway obstruction. No endoscopic surgery complication was observed. CONCLUSIONS: 1) Endoscopic supraglottoplasty is well tolerated and does not present complications when used in children; 2) Endoscopic supraglottoplasty was efficient in the treatment of children with severe laryngomalacia and in without neurological impairment; however, supraglottoplasty did not resolve airway obstruction in children with neurological impairment.

Thyroid alar cartilage laryngotracheal reconstruction for severe pediatric subglottic stenosis

BACKGROUND/PURPOSE

Laryngotracheoplasty has become an accepted treatment alternative for subglottic stenosis. However, the best autogenous material for laryngotracheoplasty remains controversial. Autogenous superior thyroid alar cartilage (TAC) has been used successfully in single stage laryngotracheal reconstruction in children with subglottic stenosis.

METHODS

This is a retrospective study of 6 children (mean age, 16.6 months) undergoing TAC graft laryngotracheoplasty between September 1995, and June 1999. Two children had immediate tracheal intubation for congenital subglottic stenosis. Four others had previous tracheostomy: 3 for severe postintubation subglottic stenosis and 1 for congenital subglottic stenosis. After an anterior cricoid split, a piece of TAC was sutured between the cut ends of the cricoid, with the graft perichondrium facing intraluminally. Endotracheal intubation was maintained postoperatively.

RESULTS

Four children underwent successfully extubation 9 to 21 days (mean, 15.5 days) postoperatively. Two required tracheostomy, which was maintained because of severe laryngomalacia and laryngotracheobronchomalacia. One child was treated with CO2 laser because of symptomatic recurrence of the subglottic stenosis 3 weeks after the surgery; another required fundoplication for gastroesophageal reflux 12 months after laryngotracheoplasty. There were no donor site complications in any of the 6 cases. Repeat laryngoscopy and bronchoscopy showed a patent subglottic airway. All of them are without symptoms after a mean follow-up of 26 months.

CONCLUSIONS

(1) This preliminary experience indicates that the TAC graft technique is a viable option for laryngotracheal reconstruction; (2) the TAC graft has significant advantages, including a single operative incision and absence of donor-site morbidity.

IL-13-mediated worm expulsion is B7 independent and IFN-gamma sensitive

B7 costimulation is a required component of many type 2 immune responses, including allergy and protective immunity to many nematode parasites. This response includes elevations in Th2 cytokines and associated effector functions including elevations in serum IgG1 and IgE and parasite expulsion. In studies of mice infected with Trichuris muris, blocking B7 ligand interactions inhibited protective immunity, suppressed IL-4 production, and enhanced IFN-gamma production, but unexpectedly did not inhibit production of the Th2 cytokine, IL-13. Blocking both IFN-gamma and B7 restored protective immunity, which was IL-13 dependent, but did not restore IL-4 or associated IgE responses. Although IL-13 was required for worm expulsion in mice in which both IFN-gamma and B7 were blocked, IL-4 could mediate expulsion in the absence of both IL-13 and IFN-gamma. These studies demonstrate that 1) B7 costimulation is required to induce IL-4, but not IL-13 responses; 2) IL-13 is elevated in association with the IFN-gamma response that occurs following inhibition of B7 interactions, but can only mediate IL-4-independent protection when IFN-gamma is also inhibited; and 3) increased IL-13 production, in the absence of increased IL-4 production, is not associated with an IgE response, even in the absence of IFN-gamma.

Stat6 regulation of in vivo IL-4 responses

Although in vitro development of a Th2 response from naive CD4+ T cells is Stat6 dependent, mice immunized with a goat Ab to mouse IgD have been reported to produce a normal primary IL-4 response in Stat6-deficient mice. Experiments have now been performed with mice immunized with more conventional Ags or inoculated with nematode parasites to account for this apparent discrepancy. The ability of an immunogen to induce a primary in vivo IL-4 response in Stat6-deficient mice was found to vary directly with its ability to induce a strong type 2 cytokine-biased response in normal mice. Even immunogens, however, that induce strong primary IL-4 responses in Stat6-deficient mice induce poor memory IL-4 responses in these mice. Consistent with this, Stat6-deficient CD4+ T cells make relatively normal IL-4 responses when stimulated in vitro for 3 days with anti-CD3 and anti-CD28, but poor IL-4 responses if they are later restimulated with anti-CD3. Thus, Stat6 signaling enhances primary IL-4 responses that are made as part of a type 0 cytokine response (mixed type 1 and type 2) and is required for normal development or survival of Th2 memory cells.

Stat6 signaling promotes protective immunity against Trichinella spiralis through a mast cell- and T cell-dependent mechanism

Studies in mice infected with the gastrointestinal nematode parasite Nippostrongylus brasiliensis demonstrated that IL-4/IL-13 activation of Stat6 suppresses development of intestinal mastocytosis and does not contribute to IL-4/IL-13 production, but is still essential for parasite expulsion. Because expulsion of another gastrointestinal nematode, Trichinella spiralis, unlike N. brasiliensis expulsion, is mast cell dependent, these observations suggested that T. spiralis expulsion would be Stat6 independent. Instead, we find that Stat6 activation by IL-4/IL-13 is required in T. spiralis-infected mice for the mast cell responses that induce worm expulsion and for the cytokine responses that induce intestinal mastocytosis. Furthermore, although IL-4 induces N. brasiliensis expulsion in the absence of B cells, T cells, and mast cells, mast cells and T cells are required for IL-4 induction of T. spiralis expulsion. Thus, Stat6 signaling is required for host protection against N. brasiliensis and T. spiralis but contributes to expulsion of these two worms by different mechanisms. The induction of multiple effector mechanisms by Stat6 signaling provides a way for a cytokine response induced by most gastrointestinal nematode parasites to protect against most of these parasites, even though different effector mechanisms are required for protection against different nematodes.

[Thoracoscopy with mediastinoscope in pediatric complicated parapneumonic effusion]

OBJECTIVE: To evaluate our experience with thoracoscopy with small mediastinoscope in complicated parapneumonic effusion in children.METHODS: From July 1995 to June 1997, seven children with complicated parapneumonic pleural effusion underwent thoracoscopy with mediastinoscope at Hospital de Clínicas de Porto Alegre. The procedure was carried out with a small mediastinoscope built in our hospital.RESULTS: There were six girls and one boy. The procedure was preformed under general anesthesia, without selective intubation. Six patients had previous intercostal tube drainage; one underwent thoracoscopy as a primary procedure. No complication was observed after the procedure. During follow-up, two children underwent pleurotomy due to residual pleural effusion with persistent fever; two others presented asymptomatic small pleural effusion.CONCLUSION: Thoracoscopy with small mediastinoscope is safe, efficient and without severe complications. It is very useful to remove loculated complicated parapneumonic effusion at fibrinopurulent stage and to enable lung expansion.

Characterization of T cell-mediated responses in nonhealing and healing Leishmania major infections in the absence of endogenous IL-4

IL-4 drives polarized Th2 responses, and differentiating Th2 cells down-regulate their sensitivity to IL-12. Therefore, the failure of BALB/c mice to heal Leishmania major infection could be due to an IL-4-dependent biased Th2 response or to a reduced capacity of Leishmania-specific Th cells to respond to IL-12. We examined the ability of CD4+ Th cells from L. major-infected wild-type and IL-4-deficient BALB/c mice to respond to IL-12. We show that the inability of normal and IL-4-deficient BALB/c mice to heal L. major infections is due to their inability to generate effective Th1 responses and not to persistent IL-4-dominated Th2 responses. Redirection of immune responses in vivo by administration of IL-12 or anti-CD4 mAb treatment in the early phase of infection (+/-12 days) allows both normal and IL-4-deficient BALB/c mice to heal their lesions by allowing them to develop an efficient Th1 response regardless of the presence or the absence of IL-4. Finally, on a population level, Ag-specific Th cells from infected animals induced to heal display a strongly elevated response to IL-12.

Characterization of T cell-mediated responses in nonhealing and healing Leishmania major infections in the absence of endogenous IL-4

IL-4 drives polarized Th2 responses, and differentiating Th2 cells down-regulate their sensitivity to IL-12. Therefore, the failure of BALB/c mice to heal Leishmania major infection could be due to an IL-4-dependent biased Th2 response or to a reduced capacity of Leishmania-specific Th cells to respond to IL-12. We examined the ability of CD4+ Th cells from L. major-infected wild-type and IL-4-deficient BALB/c mice to respond to IL-12. We show that the inability of normal and IL-4-deficient BALB/c mice to heal L. major infections is due to their inability to generate effective Th1 responses and not to persistent IL-4-dominated Th2 responses. Redirection of immune responses in vivo by administration of IL-12 or anti-CD4 mAb treatment in the early phase of infection (+/-12 days) allows both normal and IL-4-deficient BALB/c mice to heal their lesions by allowing them to develop an efficient Th1 response regardless of the presence or the absence of IL-4. Finally, on a population level, Ag-specific Th cells from infected animals induced to heal display a strongly elevated response to IL-12.