Increased distribution and expression of CD64 on blood polymorphonuclear cells from patients with the systemic inflammatory response syndrome (SIRS)

Abstract

Evidence is growing to suggest that the multiple organ damage of the systemic inflammatory response syndrome (SIRS) arises from the untoward activity of blood polymorphonuclear cells (PMNs), which upon activation acquire the IgG high affinity receptor, CD64. In the current study, flow cytometry was used to assess the prevalence of CD64-bearing PMNs and the intensity of expression of CD64 in whole blood samples from 32 SIRS patients, 11 healthy normal subjects and from eight non-SIRS patients in the intensive care unit (ICU). The percentage of PMNs expressing CD64 was higher in SIRS patients (mean 65%) than in non-SIRS patients (mean 42%; P < 0.02) and in healthy controls (mean 19%; P < 0.001) and was particularly evident in patients with SIRS and sepsis (mean 71%; P < 0.02) as opposed to SIRS alone (mean 55%). There were more CD64 molecules expressed on PMNs from patients with SIRS (median 1331 molecules/cell) in comparison with PMNs from healthy subjects (median 678 molecules/cell; P < 0.01). The highest intensity of CD64 expression was associated with PMNs from patients with both SIRS and sepsis. Functional studies revealed that the supranormal binding of PMNs from patients with SIRS to endothelial monolayers treated with TNFalpha was impeded by anti-CD64 antibodies (mean 24% inhibition; P < 0.01). Monitoring the distribution of CD64+ PMNs and their level of CD64 expression could be of assistance in the rapid discrimination of patients with SIRS from other ICU patients and in the identification of PMNs which are likely to participate in the pathological manifestations of the disease.

Fig. 1

Prevalence of CD64-bearing polymorphonuclear cells in the blood of patients with SIRS. Flow cytometric analysis was performed on blood PMNs from 32 patients with SIRS, eight non-SIRS patients in the intensive care unit (ICU) and 11 healthy control subjects. Results are expressed as the percentage of CD64⁺ cells. Horizontal bars represent the mean values. The percentage of CD64-bearing PMNs was far higher in SIRS blood than in the other two groups of subjects (P < 0·001), as assessed by analysis of variance using Bonferroni's correction.

Fig. 2

Polymorphonuclear cells expressing CD64 are a particular feature of SIRS patients with sepsis. Fourteen SIRS patients without sepsis and 18 SIRS patients with sepsis were examined for their distribution of CD64-bearing PMNs. Results are expressed as the percentage of CD64⁺ ve cells. Horizontal bars represent the mean values. Within the sepsis group, patients with Gram-positive, Gram-negative or fungal infections are indicated. There were more CD64⁺ PMNs in the SIRS patients with sepsis than in SIRS patients without sepsis (P < 0·02 by two-tailed Student's t-test). ▵, SIRS; □, Gram-negative; ○, Gram-positive; ▪, fungal.

Fig. 3

Quantitative expression of CD64 molecules on the surface of polymorphonuclear cells. Results are expressed as the number of CD64 molecules/PMN in samples obtained from 32 patients with SIRS, eight non-SIRS patients in the intensive care unit (ICU) and 11 healthy control subjects. Horizontal bars indicate the median values. There were more CD64 molecules on the PMNs of patients with SIRS in comparison with PMNs from healthy control subjects (P < 0·01 using the Kruskal–Wallis statistic with Dunn's muliple comparison test).

Fig. 4

Increased numbers of CD64 molecules are expressed preferentially on polymorphonuclear cells from SIRS patients with sepsis. Results are of the median number of CD64 molecules on PMNs from 18 SIRS patients with sepsis and 14 SIRS patients without sepsis. Horizontal bars indicate the median values. Within the sepsis group patients with Gram-positive, Gram-negative or fungal infections are indicated. Patients with sepsis had more CD64 molecules on their surface than PMNs from the non-sepsis group (P < 0·01) as determined by the Mann–Whitney test. ▵, SIRS; □, Gram-negative; ○, Gram-positive; ▪, fungal.

Fig. 5

Anti-CD64 antibodies impair the attachment of PMNs from SIRS patients to endothelial cells treated with TNFα. In each of six experiments, PMNs from a different patient with SIRS were treated with anti-CD64 antibodies and other aliquots of the cells with control isotype-matched antibodies before being overlaid onto endothelial cells that had been stimulated with 10 U/ml TNFα for 5 h. Results are expressed as the percentage inhibition of PMN adhesion induced by the anti-CD64 antibodies, relative to the control antibodies. In experiments 1, 2 and 5 the PMNs were from SIRS patients with sepsis and in the remaining experiments from SIRS patients without sepsis. Overall, the anti-CD64 antibodies produced a mean 24% inhibition of PMN attachment (P < 0·02 by the Student's t-test).