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Reduced expression of neutrophil CD11b and CD16 after severe traumatic injury
C White-Owen1, J W Alexander, G F Babcock
1Department of Surgery, University of Cincinnati, Ohio.
Abstract:
Overwhelming sepsis continues to be a major source of morbidity and mortality in patients who have sustained severe traumatic injury. Recently, much interest has been focused on the role of the peripheral blood neutrophil (PMN) in infections in these patients. Two surface receptors, CD11b (CR3) and CD16 (Fc gamma RIII), are thought to participate in bacterial phagocytosis and are both present on greater than 85% of normal PMNs. We have previously shown that cells that lack both of these receptors have markedly reduced phagocytic function. The purpose of this study was to determine the effect of severe trauma on the expression of these PMN receptors. Twenty severe trauma patients, age 19-70 years, presenting with an initial APACHE II score of greater than or equal to 10 were arbitrarily divided into two groups to define severity of injury: Group A, initial APACHE II of 10-18 (n = 11) and Group B, initial APACHE II of 19-25 (n = 9). Blood was obtained on admission, on Day 3, and weekly thereafter. PMNs were stained with fluorochrome-labeled monoclonal antibodies directed against CD11b and CD16 and then analyzed by flow cytometry. Controls consisted of 14 normal adults, age 20-65 years. The percentage and absolute numbers of CD11b+/CD16+ PMNs were determined for each patient or control sample. ANOVA and multiple comparison of variables (P = 0.05) were performed for each week. Values for Group A were different from controls at Weeks 0, 1, and 3. Values for Group B were significantly lower than those of controls at all weeks.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Severe trauma significantly reduces expression of CD11b and CD16 receptors on neutrophils, impairing bacterial phagocytosis in trauma patients. This receptor downregulation correlates with injury severity, impacting infection risk.
Area of Science:
- Immunology
- Trauma Surgery
- Critical Care Medicine
Background:
- Sepsis is a major cause of death in severe trauma patients.
- Peripheral blood neutrophils (PMNs) play a key role in combating infections in trauma.
- CD11b and CD16 are crucial surface receptors on PMNs for bacterial phagocytosis.
Purpose of the Study:
- To investigate the impact of severe trauma on the expression of CD11b and CD16 receptors on PMNs.
- To correlate PMN receptor expression levels with injury severity.
Main Methods:
- Flow cytometry was used to analyze CD11b and CD16 expression on PMNs from 20 severe trauma patients and 14 healthy controls.
- Patients were grouped by APACHE II scores (10-18 for Group A, 19-25 for Group B).
- Blood samples were collected at admission, Day 3, and weekly thereafter.
Main Results:
- Trauma patients showed altered CD11b+/CD16+ PMN expression compared to controls.
- Group A (moderate injury) showed differences at Weeks 0, 1, and 3.
- Group B (severe injury) exhibited significantly lower CD11b+/CD16+ PMN levels at all measured time points.
Conclusions:
- Severe trauma significantly downregulates CD11b and CD16 expression on PMNs.
- Reduced expression of these phagocytic receptors may contribute to increased infection susceptibility in trauma patients.
- The degree of receptor downregulation appears to correlate with injury severity.