BACKGROUND: Mannose-binding lectin (MBL) plays an important role in host defense by activating the complement cascade. OBJECTIVE: Three children with a history of recurrent infections since infancy were found to have MBL deficiency associated with a neutrophil chemotactic unresponsiveness specific to C5a. We have studied the genomic sequence of the C5a receptor (C5aR) in 2 of the subjects to determine whether this unresponsiveness was due to a genetic mutation or to aberrant complement activation associated with the MBL deficiency. METHODS: MBL genotype analysis was performed by PCR-based methods with use of specific primers and restriction enzymes to detect the 3 previously reported mutations. Expression of C5aR was analyzed by flow cytometry. The C5aR gene was amplified from the patient's genomic DNA by PCR and sequenced by standard procedures. RESULTS: C5aR was found to be expressed normally on the neutrophils of one of the subjects. Sequence analysis of the C5aR gene revealed a point mutation that substituted threonine at position 261 for alanine in one patient but no abnormality in the other, suggesting gene polymorphism. Treatment of 2 patients with granulocyte-colony stimulating factor corrected the neutrophil chemotactic abnormality in vitro and induced a significant clinical improvement. CONCLUSION: MBL deficiency can be associated with neutrophil chemotactic unresponsiveness to C5a and it is clinically manifested by recurrent and chronic infections. Treatment of these patients with granulocyte colony-stimulating factor results in normalization of neutrophil chemotaxis against C5a and significant clearing of infections.
BACKGROUND:Mannose-binding lectin (MBL) plays an important role in host defense by activating the complement cascade. OBJECTIVE: Three children with a history of recurrent infections since infancy were found to have MBL deficiency associated with a neutrophil chemotactic unresponsiveness specific to C5a. We have studied the genomic sequence of the C5a receptor (C5aR) in 2 of the subjects to determine whether this unresponsiveness was due to a genetic mutation or to aberrant complement activation associated with the MBL deficiency. METHODS:MBL genotype analysis was performed by PCR-based methods with use of specific primers and restriction enzymes to detect the 3 previously reported mutations. Expression of C5aR was analyzed by flow cytometry. The C5aR gene was amplified from the patient's genomic DNA by PCR and sequenced by standard procedures. RESULTS:C5aR was found to be expressed normally on the neutrophils of one of the subjects. Sequence analysis of the C5aR gene revealed a point mutation that substituted threonine at position 261 for alanine in one patient but no abnormality in the other, suggesting gene polymorphism. Treatment of 2 patients with granulocyte-colony stimulating factor corrected the neutrophil chemotactic abnormality in vitro and induced a significant clinical improvement. CONCLUSION:MBL deficiency can be associated with neutrophil chemotactic unresponsiveness to C5a and it is clinically manifested by recurrent and chronic infections. Treatment of these patients with granulocyte colony-stimulating factor results in normalization of neutrophil chemotaxis against C5a and significant clearing of infections.
Authors: M Cedzynski; J Szemraj; A S Swierzko; L Bak-Romaniszyn; M Banasik; K Zeman; D C Kilpatrick Journal: Clin Exp Immunol Date: 2004-05 Impact factor: 4.330