CULTURED PERIPHERAL-BLOOD MONONUCLEAR-CELLS DERIVED FROM PATIENTS WITH ACUTE SEVERE ASTHMA (STATUS-ASTHMATICUS) SPONTANEOUSLY ELABORATE A NEUTROPHIL CHEMOTACTIC ACTIVITY DISTINCT FROM INTERLEUKIN-8

Peripheral blood mononuclear cells (PBMC) isolated from patients with acute severe asthma on the day of admission to hospital were cultured in vitro in serum-free medium in the absence of mitogenic stimulants for as long as 72 h. PBMC isolated from control groups (mild asthma, chronic obstructive airway disease, normal subjects) were cultured in a similar fashion. After incubation, the culture supernatants were tested for neutrophil chemotactic activity (NCA) using a modified Boyden chamber technique. PBMC from patients with acute severe asthma elaborated significantly greater amounts of NCA into the culture supernatants as compared with all three control groups (p < 0.01). The amounts of PBMC-derived NCA from the same patients after 7 days of hospital therapy and clinical improvement were reduced (p < 0.01). A correlation was observed between the extent of reduction in spontaneous release of NCA by PBMC derived from patients with acute severe asthma and the degree of clinical improvement of their asthma (p < 0.02). Both monocytes and lymphocytes, when cultured separately, released NCA in amounts sufficient to account for the total activity released by unfractionated PBMC. NCA in PBMC culture supernatants accumulated progressively with time, a process inhibited in a dose-dependent fashion by cycloheximide. The amounts of NCA in culture supernatants did not correlate with the concentrations of histamine in lysates of the PBMC prepared just prior to culture. These observations exclude the possibility that the NCA may have been derived from basophils or plasma contaminating the PBMC preparations. NCA from PBMC from patients with acute severe asthma and from normal control subjects was concentrated and characterized by gel filtration and chromatofocusing. A single peak of NCA corresponding to a molecular size of 12 to 25 kD and a pl of 8.3 was observed in the concentrated supernatant derived from culture of PBMC derived from the patients with acute severe asthma but not that from normal control subjects. This activity was not reduced by the addition of a monoclonal antibody to interleukin-8 (NAP-1), which, under identical conditions, abolished the chemotactic activity of human recombinant interleukin-8 at an equivalent concentration. A second peak of neutrophil chemotactic activity corresponding to a molecular size of 40 to 60 kD was observed in comparable amounts in concentrated PBMC culture supernatants from both patients with acute severe asthma and normal control subjects. This study demonstrates that mononuclear cells in the peripheral blood of patients with acute severe asthma spontaneously elaborate a neutrophil chemotactic activity that is distinct from interleukin-8 and that might be implicated in the pathogenesis of this disease.