Distribution characteristics of immunoglobulin-secreting cells in adenoids. Relationship to age and disease

Forty-four adenoids and 52 palatine tonsils from 71 children and adolescents (age 3-21 years) undergoing surgery because of adenoidal hypertrophy or recurrent tonsillitis were examined for the presence of immunoglobulin-secreting cells (ISC) employing an enzyme-linked immunospot assay (ELISPOT). ISC constituted less than 2% of the mononuclear cell population. Adenoids contained IgG, IgA, and IgM ISC in significantly lower numbers than palatine tonsils. The predominant isotype of the ISC was IgG, in adenoids accounting for 62% of the ISC and in palatine tonsils for 73%. The relative numbers for IgA and IgM ISC were similar. A significant correlation existed between autologous adenoids and palatine tonsils for the numbers of IgA and IgM ISC, but not for the numbers of IgG cells. These observations suggest that, adenoid and palatine tonsils display similar immunoglobulin distribution patterns within a single individual. However, individuals with hypertrophied adenoids exhibited a numeric decrease in IgG ISC with increasing age (P less than 0.01). Both lymphoid tissues may be involved in mucosal immune defense.

Active respiratory syncytial virus purified by ion-exchange chromatography: characterization of binding and elution requirements

Two viruses, respiratory syncytial virus (RSV) and vesicular stomatitis virus (VSV) were used to evaluate viral purification by an affinity resin column (Matrex Cellufine Sulfate (MCS); Amicon Division, WR Grace & Co.). Viable RSV was purified significantly from crude cell lysate by a single pass through a column containing the anionic MCS resin. Most cell protein and albumin eluted from the MCS resin with phosphate buffered saline (PBS) but RSV eluted at high ionic strength, i.e., greater than or equal to 0.6 M NaCl. Further purification was possible by sucrose step gradient centrifugation. The RSV prepared by column purification or by column plus sucrose gradient separation was both intact and infective. RSV and pure samples of VSV were used to optimize ionic strength and salts for elution from the MCS column: 0.8 M NaCl removed most of the viral protein. The capacity of the MCS gel for RSV or VSV was found to be about 0.6-0.8 mg viral protein per ml of hydrated resin. Detergent-solubilized viral membrane proteins bound to the MCS resin in 0.145 M NaCl and eluted with higher salt concentrations. Thus, this resin also may be a useful aid for relatively gentle purification of these proteins.

The role of IgE-mediated hypersensitivity in the development of otitis media with effusion

The potential mechanisms of IgE-mediated hypersensitivity in OME have been reviewed. Two important questions were addressed at the beginning of this manuscript: (1) is OME an allergic disease, or (2) is OME a complication of an allergic disease in another part of the respiratory system? In regard to the first question, recurrent OME is associated with allergic rhinitis in about one-third of the studied population. However, of the patients who do have allergic rhinitis, in the great majority of children the middle ear mucosa is not the target organ. Rather, there appears to be increasing evidence that with both nasal provocation and natural antigen provocation in children during a normal allergen season, eustachian tube function is altered by nasal allergy. Whether this is truly physiologic or an artificial phenomenon cannot be determined at this time, as it is not absolutely clear whether the nine-step eustachian tube function test currently performed is really a measure of eustachian tube dysfunction, despite its forming the basis of all studies published so far, although one must conclude from current data that allergic rhinitis can produce eustachian tube dysfunction; there have been no cases in these studies in which allergic rhinitis produced otitis media. However, eustachian tube dysfunction is one of the major precursors in the development of OME. We believe that the anatomic part of the upper respiratory tract involved in the IgE-mediated hypersensitivity is most likely the mucosa of the nasopharyngeal portion of the eustachian tube. Inasmuch as total nasal obstruction, at least in adults, does not produce eustachian tube dysfunction in the great majority of cases, it is proposed that eustachian tube dysfunction that follows nasal provocation and occurs during the normal allergy season does so as a result of the transport of mediators of inflammation from inflammatory cells in the nasal mucosa via the nasal mucociliary system to the nasopharyngeal orifice of the eustachian tube. The role of food allergy is still problematic, but this author suggests that there is some supportive evidence that food immune complexes, particularly with dairy products, may play a role, especially in the otitis-prone child under the age of 2 years.(ABSTRACT TRUNCATED AT 400 WORDS)

Mucosal immunology of the upper respiratory tract

The palatine tonsils and nasopharyngeal adenoids represent the predominant immunocompetent tissue of the upper respiratory tract. Its major function is as a first line of defense against viral, bacterial, and food antigens that enter the upper aerodigestive system. Another major function of the tonsils and adenoids is to supply the local mucosal immune system of the upper respiratory tract with dimeric IgA-producing B cells. Secretory IgA has particular hydrophilic properties and is capable of preventing adsorption and penetration of bacteria and/or viruses into the upper respiratory tract mucosa. In addition, the role of the indigenous flora of the upper respiratory tract, particularly the viridans streptococci has been emphasized as providing a valuable source of bacterial interference to the colonization of potential pathogens.

Role of Epstein-Barr virus and interleukin 6 in the development of lymphomas of human origin in SCID mice engrafted with human tonsillar mononuclear cells

Mice with severe combined immunodeficiency were inoculated intraperitoneally with 50 x 10(6) human tonsillar mononuclear cells (hu-TMCs) from Epstein-Barr virus (EBV) antibody seropositive or seronegative human subjects. Between 5 and 11 weeks later, 29.4% (10/34) of mice injected with hu-TMCs from EBV seropositive donors, but none of 34 animals receiving hu-TMCs from EBV seronegative donors, developed intraabdominal and/or intrathoracic tumours (P, 0.002). By means of in situ hybridization using alpha satellite DNA from human chromosome 17, all tumours produced after cell transfer from EBV seropositive donors were identified to be of human origin. Histologically the tumours resembled large cell lymphomas; the EBV genome was detected by in situ hybridization and EBV nuclear antigen by immunofluorescence in these tumours. The tumours were poly- or oligoclonal, and stained for human IgG and IgM, and less frequently IgA and IgD. Serum levels of human immunoglobulin in animals developing human tumours were significantly higher than in reconstituted mice without tumours and the sera exhibited polyoligo- or monoclonality in immunoelectrophoresis. Human interleukin 6 was detected in the serum of six of 10 animals with human lymphomas, but not in any animals without human lymphoma.

Recurrent otitis media with non-typable Haemophilus influenzae: the role of serum bactericidal antibody

The effect of serum bactericidal antibody on colonization with non-typable Haemophilus influenzae (NTHI) was studied in 26 children. Serum bactericidal antibody did not prevent colonization with NTHI in the nasopharynx. Antibody was present in 53% before, 91% during and 100% after documented colonization of the nasopharynx with NTHI. In addition, 5 children with recurrent otitis media with effusion (OME) due to NTHI were observed for bactericidal serum antibody during a 4-year period. Bactericidal antibody against the causative NTHI strain was not detected in the acute sera of any patient during each episode, but was observed in the convalescent sera of all of the patients. The bactericidal antibody in the convalescent serum did not appear to be protective against colonization and recurrence of disease by a different heterologous strain of NTHI. However, bactericidal antibody was augmented in some cases by a heterologous infection with NTHI. We confirmed the emergence of new strains of NTHI with DNA fingerprinting and outer membrane protein (OMP) analysis. The data suggest that the immune response to NTHI in OME is usually strain-specific, and furthermore, the results demonstrate that strain-specific bactericidal antibody does not prevent colonization in the nasopharynx with the homologous or heterologous bacterial strains. In general, bactericidal antibody is not cross-protective against heterologous strains of NTHI causing a second or third episode of otitis media with NTHI.

A comparison of netilmicin and tobramycin therapy in patients with renal impairment

We evaluated the toxicity and efficacy of netilmicin and tobramycin in 89 older adults with serious bacterial infections and pre-existing renal impairment in a prospective, blinded, randomized trial. Complete resolution or improvement of infection occurred at 34/36 (94%) evaluable sites in netilmicin-treated patients and at 26/31 (84%) evaluable sites in tobramycin-treated patients. 10/44 (23%) netilmicin- and 7/45 (16%) tobramycin-treated patients experienced nephrotoxicity during treatment. The mean serum creatinine level improved significantly at the end of therapy compared to pre-treatment in those patients who did not experience nephrotoxicity in both treatment groups. 5/19 (26%) netilmicin-treated patients and 2/18 (11%) tobramycin-treated patients assessable for ototoxicity experienced decrements in auditory thresholds. Ototoxic netilmicin-treated patients had higher serum netilmicin levels than did non-ototoxic patients. Patients who experienced ototoxicity were not more likely to have experienced nephrotoxicity. The rates of toxicity were not statistically different and were similar to those seen in studies of patients with normal pre-treatment renal function.

The role of autonomic nervous system and inflammatory mediators in nasal hyperreactivity: a review

The last decade has seen a marked increase in the number of otolaryngologists-head and neck surgeons who have been trained to perform rhinologic surgery. This includes both rhinoseptoplasty and endoscopic sinus surgery. A better understanding of the pathophysiology of rhinitis and sinusitis has also kept pace with this rapid expansion of surgical intervention. For example, significant advances have taken place in our knowledge of the local immune system in the nose, particularly in regard to mucosal and submucosal mast cells and the development of protective antibodies in the nasal mucosa against viral and bacterial infections. We have far more understanding of the complex innervation of the blood vessels and glands in the nasal mucosa and their receptors, and, most recently, a tremendous increase of scientific data has accumulated on the effect of neuropeptides on the nasal mucous membrane. It is imperative that rhinologic surgeons have an understanding and appreciation of the complex patterns of sensory and autonomic innervation of the nose to better evaluate the medical, allergic, and surgical treatment of acute and chronic rhinitis and sinusitis. This discussion will focus on recent advances in our understanding of the biochemical substances that are released by both the autonomic nervous system and the sensory nervous system in the nasal mucosa. The effect of these mediators on both vascular smooth muscle and the seromucinous glands of the nose will be considered. Finally, the dynamic interaction between the inflammatory mediators released by sensory nerves so-called tachykinins-- and the immune system and mast cell degranulation will be considered.

Nasopharyngeal colonization by nontypeable Hemophilus influenzae in children: the effect of serum bactericidal antibody

The effect of serum bactericidal antibody on colonization with NTHI was studied in 26 children. Serum bactericidal antibody did not prevent colonization with NTHI in the nasopharynx. Antibody was detected in 53% before, 91% during, and 100% after documented colonization. The log titer of antibody was significantly higher during (1.18 +/- 0.56), p less than 0.002; and after (1.31 +/- 0.29), p greater than 0.001 compared to before colonization (0.49 +/- 0.51). The roles of secretory IgA and normal nasopharyngeal flora in inhibiting pathogenic bacteria are discussed.

Immunologic reactivity in the middle ear in otitis media with effusion

This article reviews the immunologic reactivity in the middle ear in both the human disease and in animal models of otitis media. It differentiates the role of immune complexes in otitis media in the animal model and in the human form of middle ear inflammation. The effect of immunization of the gut on the mucosal immune system in the middle ear is briefly explored, and the source of lymphocytes that make their way into the middle ear mucosa from other parts of the mucosal immune system and systemic immune system are briefly discussed. Finally, work from the author's laboratory on the immune response of children with recurrent otitis media due to nontypable Haemophilus influenzae is summarized.

Nasopharyngeal flora in the first three years of life in normal and otitis-prone children

Nasopharyngeal carriage of the three major middle ear pathogens (Streptococcus pneumoniae, nontypeable Hemophilus influenzae, and Moraxella catarrhalis) was evaluated prospectively in a group of 110 children followed up for the first 3 years of life. The findings suggested that nasopharyngeal carriage of middle ear pathogens increases significantly during respiratory illness among the general population of young children; however, otitis-prone children demonstrated a tendency to carry nontypeable H influenzae at an unusually high rate even during health. This propensity to carry nontypeable H influenzae might explain why nontypeable H influenzae is a major cause of recurrent or chronic otitis media.

Distribution and engraftment patterns of human tonsillar mononuclear cells and immunoglobulin-secreting cells in mice with severe combined immunodeficiency: role of the Epstein-Barr virus

Tonsils seem to be the ideal source of lymphocytes seeding to the mucosa of the respiratory tract. The distribution and engraftment of human lymphocytes injected into mice with severe combined immunodeficiency (SCID) are not well understood. C.B-17 SCID mice were injected intraperitoneally with human tonsillar mononuclear cells (hu-TMC). The hu-TMC-SCID mouse chimeras were subsequently tested for the appearance and distribution of human lymphocytes tagged with H33342 and immunoglobulin-secreting cells in various systemic and mucosal immunocompetent tissues. This was done by fluorescence microscopy of tissue sections for cells supravitally stained before transfer and by an enzyme-linked immunospot assay using cells isolated from murine organs. Most importantly, engraftment of hu-TMC proved to be dependent on the presence of anti-Epstein-Barr virus (EBV) antibody in the donor. hu-TMC engrafted, in decreasing numbers, in the following systemic organs: peritoneal cavity, liver, spleen and bone marrow. Among mucosal tissues tested, hu-TMC were seen in lungs, but not in the intestines. The engraftment of hu-TMC in the lung was more extensive than that in the spleen. These studies demonstrate that hu-TMC engraft in a variety of murine tissues. The striking preference of hu-TMC for the lungs when compared to intestines suggests selective engraftment among distinct mucosal tissues. The hu-TMC-SCID mouse chimera promises to be a unique animal model to study human-mucosa-associated lymphoid cells and EBV-related lymphomagenesis and B cell tumor progression.

Human adenoidal organ culture: a model to study nontypable Haemophilus influenzae (NTHI) and other bacterial interactions with nasopharyngeal mucosa--implications in otitis media

Nontypable Haemophilus influenzae (NTHI) has become the predominant cause of both acute suppurative otitis media and chronic otitis media with effusion. It has now been well-demonstrated that both outer membrane proteins and restriction fragment analysis of the bacterial genomes of concomitant nasopharyngeal and middle ear effusion isolates of NTHI are identical. It is therefore of critical importance to understand the mechanisms whereby bacteria that are present in normal healthy children in small numbers become the predominant organism in the nasopharynx in otitis media. The studies presented here suggest that nontypable Haemophilus influenzae can effectively decrease ciliary function as measured by stroboscopic illumination of ciliary beat frequency on human adenoidal organ culture. This organism also produces significant histopathologic and ultrastructural damage to the epithelial cells and cilia of adenoid organ culture, demonstrated by both light microscopy and scanning electron microscopy. The data suggest the following hypothesis: nontypable Haemophilus influenzae can destroy mucociliary function and allow increased bacterial replication in the mucus overlying the nasopharyngeal mucosa. The mucociliary system of the eustachian tube may also be involved in a similar manner, thus allowing bacteria to enter the middle ear space via the eustachian tube.

Macrophage (monocyte)-derived mucous secretagougue (MMS) is released into the fluid of the middle ear of patients with otitis media with effusion

Macrophage (monocyte)-derived secretagogue (MMS) is a low molecular weight peptide released by activated macrophages. This substance can enhance incorporation of carbohydrates into protein and result in the production of glycoproteins. It is believed that increased glycoproteins lead to the increased tenaciousness of mucoid effusions. Sixteen of 28 middle ear effusions demonstrated significant amounts of MMS. It is suggested that MMS is produced by activated macrophages in MEE and may lead to the development of glycoprotein by secretory epithelial cells. This substance may lead to the development of the mucoid effusion in otitis media with effusion in children.

Choice of antibiotics, pharmacokinetics, and dose adjustments in acute and chronic renal failure

A multitude of antimicrobial agents have become available over the past two decades. Appropriate use of these drugs demands not only an understanding of the antimicrobial spectrum of the agent but of the necessary dose adjustments because of renal or hepatic impairment. The use of computer-assisted pharmacokinetic modeling for dosing potentially toxic drugs such as aminoglycosides and vancomycin should be utilized whenever possible.

Reducing the cost of surgical prophylaxis

A four-part program was implemented in order to control the rising cost of prophylactic antibiotics: limiting the number of cephalosporins on formulary; prohibiting the use of third- and most second-generation cephalosporins for prophylaxis; using a special order form to designate use as empiric, therapeutic, or prophylactic; and mandatory discontinuance of prophylactic antibiotics after 24 hours. The total cost for administration of prophylactic antibiotics was reduced from an average of $37.35 per case for the six months preceding the start of these restrictive policies to an average of $21.99 per case during the next twelve months. Class I and class II wound-infection rates were 2.0 per cent and 4.9 per cent, respectively, prior to the adoption of the new antibiotic practices. Comparable infection rates were 1.8 per cent and 2.1 per cent, respectively, after this program was initiated. The rising cost of antibiotic prophylaxis can be reduced without adversely affecting wound-infection rates.

Comparison of oral and aerosol ribavirin regimens in the high risk elderly

A comparison of different regiments of ribavirin (R), administered either orally or by aerosol, was performed in 16 elderly subjects (13 men, 3 women, mean age 63 +/- 8 years) considered to be in the "high-risk" category for complications from influenza as defined by the Centers for Disease Control. The subjects were divided into four groups. Group O-600 received 600 mg orally R every 8 hours for 48 hours followed by 200 mg every 8 hours for 72 hours for a total dose of 5.4 g (22.1 mmol). Group O-800 received 800 mg oral R every 8 hours for 24 hours followed by 400 mg every 12 hours for 96 hours for a total dose of 4.1 g (22.9 mMoles). Group A-40 received R (40 mg/ml) aerosolized through a small particle aerosol generator for 6 hours every 12 hours for 96 hours, yielding an average delivered dose of 6.2 g (25.4 mMoles) R. Group A-60 received aerosolized R (60 mg/mL) for 2 hours every 8 hours for 96 hours, yielding an average delivered dose of 4.6 g (18.8 mMoles) R. No hematologic or other laboratory abnormalities were associated with any of the regimens. Group O-800 and O-600 reached mean peak plasma R levels of 11.8 microM and 5.3 microM, respectively, after 18 hours of therapy. Subsequent administration of 20 mg R every 8 hours was sufficient to maintain a plasma R level greater than 7 microM. Among the aerosol groups, group A-40 approached steady state plasma R levels (8-10 microM) more quickly than group A-60.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of the epidemiology and transmission of nontypable Haemophilus influenzae in children with otitis media by comparison of total genomic DNA restriction fingerprints

It is assumed that the causative bacteria in children suffering from otitis media reach the middle ear via the eustachian tube. The purpose of this investigation was to use endonuclease restriction of bacterial chromosomal DNA to compare isolates of nontypable (NT) Haemophilus influenzae obtained from the nasopharynx and from middle ear (ME) effusions of patients with otitis media. Strains of NT H. influenzae were isolated from the nasopharynx (NP) and affected ME from a group of 13 unrelated children with otitis media with effusion (OME). For 12 of these children, identical strains were isolated from the NP and ME in a first episode of OME. Each of these 12 sets differed from the other 11. Six of these children suffered from a second episode of OME with NT H. influenzae. Five of these children with recurrence again had identical NP and ME strains. These results suggest that at the time of an episode of OME, there is one predominant strain of NT H. influenzae that colonizes both the NP and ME. The strains of NT H. influenzae isolated from all six of the second episodes were different from strains from the first episode, indicating turnover of the predominant strain in the NT H. influenzae population between episodes. When we investigated three siblings with concurrent episodes of OME, we found that they shared several similar strains of NT H. influenzae, thereby demonstrating that within a family, transmission of NT H. influenzae from child to child is possible. These results from DNA fingerprinting were essentially identical when compared with results from outer membrane protein subtyping performed on the same set of strains. The analysis of endonuclease restriction patterns of total genomic DNA provides a sensitive measure of genetic dissimilarity between strains and represents an easily applicable method for epidemiological and transmission studies of bacterial infections associated with NT H. influenzae.

Restriction fragment mapping of nontypable haemophilus influenzae: a new tool to study this middle ear pathogen

Isolates of nontypable haemophilus influenzae (NTHI) recovered from paired nasopharyngeal (NP) and middle ear (ME) fluid cultures performed simultaneously on seven children with otitis media with effusion (OME) were studied by analysis of the restriction fragment patterns produced from total genomic DNA. This method provides a sensitive measure of the genetic similarities between strains. In the seven pairs examined, the NP and ME strains were indistinguishable from one another, whereas each pair was distinct from the other, except for two siblings in whom all four strains were identical. This information provides evidence that the pathogenesis of OME caused by NTHI involves spread of the bacteria from NP to the ME. Analysis of paired NP and ME isolates from three children with recurrent OME caused by NTHI indicated that the second episode was caused by the reinfection with a different strain rather than persistence and reemergence of the first strain. Finally, DNA analysis of strains from two siblings with concurrent OME suggested that person-to-person transmission of NTHI can occur among children. These findings suggest that at any one time the NTHI population in the NP is relatively homogenous, at least at the time of acute upper respiratory disease. Our observation that the strains present at the second episode of otitis media were different than the strains present in the first episode is consistent with strain replacement in the NP. Restriction fragment mapping analysis of genomic DNA of NTHI could provide a powerful tool for investigating the rate of turnover of the NTHI population in the NP.

Eustachian tube dysfunction in children with ragweed hayfever during natural pollen exposure

The role of upper respiratory allergy in the pathogenesis of otitis media with effusion (OME) is an interesting but still unresolved issue. In order to investigate this further, fifteen children with ragweed hayfever were studied for the development of eustachian tube obstruction (ETO), utilizing the nine-step pressure-swallow test, prior to, during, and after seasonal exposure to ragweed pollen. Daily symptom-medication diaries were maintained and serial physical examinations were performed. ETO was found in 60% of the ragweed sensitive children during natural pollen exposure. The development of ETO was found to correlate with ragweed skin test wheal size and daily patient symptom-medication scores (SMS) during pollen exposure. Treatment of hayfever symptoms with pseudoephedrine and/or chlorpheniramine did not prevent most patients from developing ETO. Despite the prevalence of ETO in the study group, only one child developed evidence of middle ear effusion. These findings suggest that children with ragweed hayfever develop eustachian tube (ET) dysfunction during natural pollen exposure. Seasonal allergy induced ETO is not, however, by itself sufficient to produce middle ear effusion.

Characteristics of in vitro production of mucosal antibody to respiratory syncytial virus in tonsillar tissue lymphocytes

Tonsillar lymphocytes (TL) obtained from 39 subjects were established in culture in vitro, and analyzed for respiratory syncytial virus (RSV) specific antibody synthesis after stimulation with pokeweed mitogen and live or ultraviolet light inactivated RSV. Following stimulation with the virus, IgG1, IgA, and low levels of IgG3 but no IgG2, IgG4, or IgE anti-RSV antibody could be detected in the culture supernatants. The anti-RSV antibody production in TL did not show any correlation with the preexisting levels of anti-RSV antibody in the serum of the subjects. TL collected prior to RSV infection in the community exhibited low levels of RSV antibody synthesis. On the other hand, TL obtained during the months of natural exposure to RSV exhibited significantly higher anti-RSV antibody production. TL from atopic children demonstrated IgA anti-RSV antibody more frequently and in higher content than the TL from nonatopic children. There were no significant differences in antibody production in IgG1 and IgG3 subclasses in these subjects. These observations suggest that mucosal lymphoid tissue participates in IgG1 subclass antibody production. It is also suggested that mucosal infections correlate better with local antibody synthesis than with serum antibody activity.

Eustachian tube function associated with histamine-induced and ragweed-induced rhinitis

Nasal allergies may contribute to Eustachian tube dysfunction and chronic middle ear problems. In exploring this association further, Eustachian tube function was measured in ten ragweed-allergic and eight non-allergic patients undergoing repetitive nasal provocation. Anterior nasal provocation was done using paper disks impregnated with either histamine or aqueous ragweed allergen. Increasing concentrations of the provocative agent were placed on both inferior nasal turbinates until moderate symptoms of rhinitis developed. Eustachian tube function was evaluated using the 9-step inflation-deflation tympanometric test before and immediately after each nasal challenge. Eustachian obstruction developed in 4 of 38 non-allergic ears during histamine nasal provocation. With ragweed nasal challenge, 9 of 42 allergic ears developed Eustachian tube obstruction. Four allergic ears gained Eustachian tube function despite being obstructed before the challenge. The observed changes in ear function for both groups were not significant due to variability in Eustachian response. At the concentrations which initiated symptoms of rhinitis, nasal provocation with histamine or ragweed did not consistently obstruct the Eustachian tube. We conclude that mild symptoms of allergic rhinitis may not cause significant Eustachian tube obstruction.

Leukotriene C4 release in upper respiratory mucosa during natural exposure to ragweed in ragweed-sensitive children

With high-pressure liquid chromatography and specific radioimmunoassay, the concentration of leukotriene C4 (LTC4) was measured in nasopharyngeal secretions (NPS) of groups of children with allergic rhinitis before, during, and after the ragweed-pollen season. Increase LTC4 concentrations in NPS were noted in all the children during the pollen season; the concentration of LTC4 increased from a preseasoned mean of 1.87 +/- 0.43 ng/ml to 5.52 +/- 0.7 ng/ml at the peak of the ragweed season (p less than 0.001). The mean LTC4 concentration 2 weeks after the end of the ragweed season declined only to about 4.45 +/- 1.04 ng/ml. The seasonal variation of LTC4 concentrations and symptom scores of the children paralleled the pattern of the ragweed-pollen count. All children studied were ragweed sensitive, and six children were additionally sensitive to Alternaria (mold). The mold-sensitive children demonstrated higher concentrations of LTC4 in their NPS before and continued to have high LTC4 levels after the peak ragweed season, coinciding with peaks of mold-spore counts. Data presented in this study suggest that mast cells and other target cells in the nasal mucosa of children with allergic rhinitis produce pharmacologically active mediators, such as LTC4, during natural exposure to ragweed or Alternaria.