Effects of monocyte- and macrophage-derived products on granulocyte function in asthma

Monocyte chemoattractant peptide-1 expression during cutaneous allergic reactions in mice is mast cell dependent and largely mediates the monocyte recruitment response

BACKGROUND

Macrophages and infiltrating monocytes comprise the largest population of cells within the airways of patients with allergic asthma. Both become activated and thus contribute to the pathologic features of allergic reactions, but the mechanism by which they are recruited has not been well documented.

OBJECTIVE

Our purpose was to assess the role of the CC chemokine monocyte chemotactic peptide-1 (MCP-1) in monocyte recruitment during allergic reactions in mice.

METHOD

We used immunohistochemistry and Northern blotting to assess MCP-1 expression, selective mast cell reconstitution of mast cell-deficient W/W(v) mice to demonstrate the mast cell dependence of MCP-1 expression and monocyte recruitment and neutralizing anti-MCP-1 antibodies to block monocyte recruitment during cutaneous allergic reactions.

RESULTS

MCP-1 was expressed largely by resident dermal cells within the allergic lesions at 4 hours after challenge, followed within several hours by an influx of monocytes; at 10 hours after challenge monocytes comprised a substantial proportion of the infiltrating cells at the nidus of the response. Mast cell-reconstituted, but not mast cell-deficient W/W(v) mice expressed MCP-1 transcripts and developed monocyte infiltrates after allergen challenge. Finally, anti-MCP-1 antibody treatments reduced by approximately 63% the influx of monocytes into the reaction sites.

CONCLUSIONS

These data clearly demonstrate the mast cell dependence of the MCP-1 expression and the monocyte influx and establish a substantial, but not exclusive, causal relationship between these 2 events.

Modification of surface marker expression on CD14 monocytes of allergic patients after lysis or Ficoll purification

It has been observed that peripheral blood monocytes are often in a primed or activated state in inflammatory diseases such as asthma. However, the majority of these studies have been performed using cells which have been purified by density gradient centrifugation on Percoll or Ficoll-Hypaque. Using cytofluorimetry, we compared the expression of monocyte surface markers of monocytes from untreated blood with monocytes purified by erythrocyte lysis or density centrifugation using the Ficoll technique. Monocytes from two groups of subjects were analyzed: healthy subjects and allergic patients. When compared with untreated blood, the percentage of CD16-positive cells, and the sMFI was significantly greater after monocyte purification (lysis or Ficoll). The expression of CD62L (percentage and sMFI) was modified after monocyte purification. Such modification of these two surface markers was predominantly observed on monocytes from allergic patients, and not on monocytes from healthy subjects. This study suggests that surface marker analysis should be performed on unfractionated whole blood in order to avoid modification of monocyte antigens.