Leukocyte inhibitory factor (LIF) potentiates human macrophage aggregation and activation responses to calcium ionophore A23187 and directly induces leukotriene B4 and thromboxane A2 release.

Aggregation studies have become a useful criterion for analyzing leukocyte motility and activation in vitro. The T-cell-derived lymphokine human leukocyte inhibitory factor (LIF) is a modulator of many important polymorphonuclear (PMN) functions in addition to aggregation such as chemotaxis, lysosomal degranulation, phagocytosis, bactericidal killing, augmented antibody-dependent cellular cytotoxicity (ADCC), induction of neutrophil Fc-gamma, complement type-1 and FMLP receptors, and production of superoxide and H2O2. Our investigations focused on the ability of LIF to modulate the aggregation of macrophages (MO) induced by calcium ionophore A23187. The ionophore A23187 directly induced potent aggregation of macrophages, which was markedly enhanced when the cells were pretreated with LIF. However, the addition of LIF in the absence of other costimuli did not directly induce MO aggregation. LIF was shown to enhance PMN aggregation induced by N-formyl-Met-Leu-Phe (FMLP), but did not augment the aggregation of FMLP-stimulated macrophages, indicating a cellular specificity of aggregation-inducing costimuli following LIF priming. Additional cytokines examined for possibly inducing MO aggregation were interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF), and interleukin-6 (IL-6); all proved to be incapable of inducing aggregation directly, nor did they enhance the effect of A23187 ionophore on macrophage aggregation. Additionally, we found that LIF can directly stimulate MO to activate specific pathways of the arachidonic acid cascade, inducing the synthesis and release of thromboxanes and leukotriene B4. LIF did not augment the potent ability of A23187 to induce increased production of LTB4 or TxA2 by human MO. These new results coupled with our previously published data indicate that LIF can enhance the activation of both MO and PMN leukocytes when exposed to either A23187 or FMLP, respectively. Moreover, these data suggest that LIF can contribute directly to monocyte-macrophage leukocyte activation, in addition to PMN activation, during inflammatory responses, resulting in greater cell aggregation, activation, and specific proinflammatory arachidonic acid product release.

Detection of human auto-anti-idiotypic antibodies (Ab2). I. Isolation and characterization of Ab2 in the serum of a ragweed immunotherapy-treated patient.

This study documents, by means of both solid and liquid phase assays, the presence of anti-idiotypic antibodies (Ab2) in the serum of one allergic individual undergoing ragweed immunotherapy. Serum from this individual was collected and F(ab')2 fragments specific for ragweed antigen E (AgE) were prepared (Ab1). These AgE-specific F(ab')2 Ab1, following absorption with normal immunoglobulin, were studied for their capacity to specifically bind autologous Ab2. The binding of Ab1 to Ab2 was demonstrated to be inhibitable by ragweed AgE but not by another allergen (oak) to which the patient reacted. These findings demonstrate the presence and binding specificities of Ab2 in the serum of a ragweed immunotherapy patient and may serve as a model to study the role of Ab2 in the regulation of Ab1 in allergic patients.

Detection of human auto-anti-idiotypic antibodies (Ab2). II. Generation of Ab2 in atopic patients undergoing allergen immunotherapy.

The present study demonstrates the cross-reactivity of a murine monoclonal antibody (MoAb) directed against purified ragweed antigen E (AgE) with human Ab1. This antiragweed AgE MoAb (clone SC7H.1G, IgM kappa) was used to detect Ab2 in the sera obtained from the three groups of subjects. Utilizing an ELISA assay, we found that immunoglobulins from 12 nonatopic subjects bound to a significantly greater extent to SC7H.1G (mean +/- SE; OD = 0.353 +/- 0.052) than immunoglobulins from 14 untreated ragweed atopics (OD = 0.149 +/- 0.020). However, immunoglobulins from 9 immunotherapy-treated patients (OD = 0.395 +/- 0.120) bound to the mouse anti-AgE MoAb to the same extent as nonatopic sera. Furthermore, an additional 7 patients with ragweed-allergic rhinitis were studied prospectively while undergoing immunotherapy and Ab2 levels were found to increase with time posttreatment. We also found an inverse correlation between Ab1 and Ab2 levels in the nonatopic and untreated atopic groups. These data indicate that immunotherapy stimulates the production of Ab2 in atopic patients and may be involved in the regulation of the antiragweed IgE response.

Generation of suppressor cells in atopic patients during immunotherapy that modulate IgE synthesis.

We prospectively studied the effect of ragweed immunotherapy on the generation of suppressor T cells that modulate total and antiragweed IgE production in five patients with seasonal allergic rhinitis. Suppressor T cell depletion was accomplished by treating mononuclear cells (MNCs) with the monoclonal antibody Leu 2b followed by the addition of complement. Treated and untreated MNCs were obtained before and during (6 to 24 months) immunotherapy and were cultured at 1 X 10(6) cells per milliliter for 7 days in RPM1-1640 containing 10% fetal calf serum. In order to determine the effect of ragweed antigen on IgE production, untreated or Leu 2b-depleted MNCs were incubated with short ragweed extract (SRW) (1.0 to 10 micrograms/ml) for 20 hours, washed three times, and incubated for a further 6 days. The cell-free supernatants from each were harvested and assayed for total IgE by use of a modified PRIST assay. To determine specific IgE, a modified RAST procedure was used. Total or antiragweed IgE production was calculated by subtracting preformed IgE from the total or specific IgE content in the supernatant. Depletion of Leu 2-positive cells did not affect total IgE production before immunotherapy. In contrast, a statistically significant increase was observed in total IgE 6 months (p less than 0.05) and 13 months (p = 0.005) after immunotherapy. Specific antiragweed IgE production at these times was also enhanced, but this increase did not reach statistical significance. Before immunotherapy was begun, preincubation of MNCs with SRW did not change the amount of total IgE produced.(ABSTRACT TRUNCATED AT 250 WORDS)