Patricia A. Forsythe

Monocyte chemotactic and activating factor is a potent histamine-releasing factor for basophils.

Monocyte chemotactic and activating factor (MCAF) is a recently cloned cytokine that causes chemotaxis of basophils. In our pursuit of cytokines affecting basophil function, we studied the effect of MCAF on histamine secretion from basophils. Leukocytes from 20 donors, 10 allergic and 10 normal subjects, were studied. MCAF caused dose-dependent release of histamine at concentrations of 10(-8) and 10(-7) M, and the mean release was 31.25 +/- 2.9% at the highest concentration. In the same experiments the mean histamine release by anti-IgE and histamine releasing factor (HRF) was 27.05 +/- 4% and 32.70 +/- 2.7%, respectively. All 20 subjects responded to MCAF with significant histamine release. Allergic subjects released significantly more histamine than normals in response to anti-IgE (P less than 0.01) but not to MCAF (P = 0.2) and HRF (P = 0.1). The histamine release was significantly correlated between MCAF and HRF (P less than 0.01), but not between MCAF and anti-IgE (P greater than 0.05). The histamine release by MCAF was complete within the first 3 min. MCAF-induced degranulation was a calcium-dependent process. Leukocytes depleted of monocytes responded equally well to MCAF. Using an anti-MCAF affinity column we determined that greater than 50% of HRF activity of crude PBMC supernatant could be attributed to MCAF. Thus, we established that MCAF is a potent secretagogue for basophils.

The lnterleukin-5/Receptor Interaction Activates Lyn and Jak2 Tyrosine Kinases and Propagates Signals via the Ras-Raf-1-MAP Kinase and the Jak-STAT Pathways in Eosinophils

We have shown that the interaction of interleukin (IL)-5 with the receptor activates Lyn tyrosine kinase within 1 min and Jak2 tyrosine kinase within 1-3 min. IL-5 also stimulates GTP binding to p21ras. The signal is subsequently propagated through the activation of Raf-1, MEK, and MAP kinases as shown by their increased autophosphorylation in vitro and phosphorylation in situ. Jak2 kinase has been shown to phosphorylate STAT nuclear proteins. The activation of STAT nuclear factors was studied by electrophoretic mobility shift assay using a gamma activation site (GAS) probe. We found that IL-5 induces two GAS-binding proteins in eosinophils, one of which is STAT1. We conclude that IL-5 induced signals are propagated through two distinct pathways: (1) Lyn-->Ras-->Raf-1-->MEK-->MAP kinase and (2) Jak2-->STAT1.

Measurement of histamine-releasing factor activity in individual nasal washings: Relationship with atopy, basdphil response, and membrane-bound IgE

We collected individual pools of nasal washings (NWs) from 15 allergic and 15 nonallergic subjects to determine histamine-releasing factor (HRF) activity and to ascertain the relationship of these cytokines with atopic status, basophil releasability, and cell membrane-bound IgE. NWs were concentrated, dialyzed, and assayed with basophils from a single donor. Samples from 12 of 15 allergic subjects and from all the nonallergic subjects revealed greater than or equal to 15% histamine release (HR), 33.5% +/- 21.3% (mean +/- SD) and 38.6% +/- 19.6%, respectively (p greater than 0.05). When we assayed the same samples with autologous basophils, the allergic group demonstrated higher HR than the nonallergic group (31.9% +/- 19.7% versus 4.8% +/- 4.3%; p less than 0.001). A standard lot of mononuclear cell-derived HRFs was also screened with basophils from both groups. Means for HR from basophils of allergic and nonallergic subjects were 51.9% +/- 16.7% versus 26.3% +/- 8.2%, respectively (p less than 0.001). Pretreatment of basophils with lactic acid led to abrogation of sensitivity to HRF. Acid-stripped cells incubated with sera from patients with asthma regained their capacity to release histamine. We found that HRF activity can be detected in NWs of most donors, and there is no difference among allergic and nonallergic subjects. Our results suggest that the capacity of these cytokines to induce HR depends on several factors: atopic status, basophil releasability, and membrane-bound IgE.

Sensitivity of basophils to histamine releasing factor(s) of various origin: Dependency on allergic phenotype of the donor and surface-bound IgE

Certain species of histamine-releasing factor (HRF) have been demonstrated to distinguish a select group of allergic patients from healthy subjects. An IgE-dependent mechanism of action has been suggested. The donor and IgE dependency of HRF produced by peripheral blood mononuclear cells (PBMCs) has not been clearly demonstrated. In this study, we have compared the response of basophils from normal subjects versus allergic patients with and without asthma. In addition, we have addressed the IgE dependency of HRF recovered from cultures of PBMCs, T cells, B cells, macrophages, and bronchoalveolar lavage fluid. We have demonstrated that basophils from allergic as well as normal subjects respond to PBMC-HRF. The response of basophils from allergic patients with asthma is significantly increased. This heightened response to HRF does not correlate with the severity of disease as assessed by baseline spirometry, medication, and skin test scores. Stripping of the membrane-bound IgE by incubating basophils with lactic acid causes a significant loss of sensitivity to HRF generated by PBMCs, T cells, B cells, and macrophages, as well as to HRF recovered from bronchoalveolar fluid. The loss of response can be restored by sera from patients with asthma but not from normal subjects or by myeloma IgE. In addition, poorly responsive basophils from normal subjects can be rendered sensitive by incubating with sera from patients with asthma. The capacity of a given serum from a patient with asthma to restore the response to HRF is not correlated with the total concentration of IgE in the serum.(ABSTRACT TRUNCATED AT 250 WORDS)