Related Experiment Video
Updated: Aug 11, 2026
Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells
Published on: January 29, 2014
Studies of immune response in a patient with selective complete C1q deficiency
1Department of Pediatrics, Hacettepe University Faculty of Medicine, Ankara.
Insights
A child with C1q deficiency had normal immune responses but delayed antibody production. Defective immune complex clearance, not antibody response, may cause severe infections in C1q deficiency.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Selective complete C1q deficiency is a rare complement defect.
- Understanding the immune response in C1q deficiency is crucial for managing recurrent infections.
Observation:
- A six-year-old girl with C1q deficiency exhibited normal cell-mediated immunity and antibody levels.
- Abnormal antibody kinetics were observed, with delayed peak titers after bacteriophage immunization.
Findings:
- The study did not confirm defective antibody response as the cause of severe infections.
- An alternative hypothesis suggests impaired immune complex clearance contributes to immunodeficiency in C1q deficiency.
Implications:
- Defective clearance of immune complexes may lead to severe infections in C1q deficiency by further depleting complement.
- Further research is needed to elucidate the mechanisms of infection in this rare complement defect.
Abstract:
Immune response in a six-year-old girl with a rare complement defect, namely selective complete C1q deficiency, was studied. Her cell-mediated immune response (delayed hypersensitivity skin tests, E, EAC rosettes, in vitro lymphocyte transformation with phytohemagglutinin), isohemagglutinin titers, serum immunoglobulin levels, antibody titers to tetanus, Epstein-Barr virus, keyhole limpet hemocyanin, pneumococcus and bacteriophage 0 x 174 were all normal. However, she had abnormal kinetics of the antibody response to bacteriophage following primary and secondary immunizations. Her antibody titers reached a peak four weeks after primary immunization and three weeks after secondary immunization, while the titers of controls peaked at two weeks and one week, respectively. In this study we could not prove the hypothesis that defective antibody response caused recurrent infections in this patient. An alternative hypothesis is the possible role of defective clearance of immune complexes in the development of severe infections. Patients with selective complete C1q deficiency form immune complexes with bacterial or viral antigens, thus activating the classical complement pathway. As a result, very low C1q levels decrease even further, leading to a severe immunodeficiency and recurrent infections. Future studies in this area may help to explain the mechanism(s) responsible for infections in this rare type of complement defect.
