Complete and partial deficiencies of complement factor D in a Dutch family.

A young man suffering from recurrent Neisseria infections was shown to lack detectable serum complement factor D hemolytic activity. Addition to the patient's serum of purified factor D to a final concentration of 1 microgram/ml resulted in full restoration of the activity of the alternative pathway. Using an enzyme-linked immunosorbent assay, it was shown that the patient's serum did not contain measurable amounts of factor D antigen either. The sister, the father, as well as the parents of the mother had factor D levels within the normal range, and the factor D level of the mother was decreased. The capacity of the patient's serum, at concentrations up to 5%, to promote phagocytosis of Escherichia coli by normal human granulocytes was low when compared to normal serum. Substitution of the patient's serum with purified factor D resulted in a full restoration of opsonic activity. This study describes the first complete deficiency of factor D, and demonstrates its possible relation to recurrent Neisseria infections.

Complete Clq deficiency associated with IgG multiple myeloma.

We report a case of IgG multiple myeloma with selective complete Clq deficiency. The patient was a 75-year-old Japanese woman who exhibited urticaria on the arm and an absence of serum hemolytic complement activity (CH50). Further studies revealed no vasculitis in the urticarial lesion but showed selective complete deficiency of Clq without low molecular weight Clq precipitin. Addition of highly purified Clq restored the CH50 level of the patient's serum to normal. It is suggested that this abnormality was a primary Clq deficiency. We discussed a relationship between the Clq deficiency and myeloma and reviewed the literature.

Biosynthesis of normal and low-molecular-mass complement component C1q by cultured human monocytes and macrophages.

High levels of low-molecular-mass complement component C1q (LMM-C1q), a haemolytically inactive form of C1q, are found in serum of individuals with inherited complete (functional) C1q deficiency and in serum of patients with systemic lupus erythematosus, whereas lower levels are present in normal serum [Hoekzema, Hannema, Swaak, Paardekooper & Hack (1985) J. Immunol. 135, 265-271]. To investigate whether LMM-C1q is a (by-)product of C1q synthesis or the result of degradation of C1q, cultures of blood monocytes and of alveolar macrophages, which secrete functional C1q, were studied. A considerable portion of C1q-like protein secreted by these cells was found to be LMM-C1q. In contrast with the C1q fragments that resulted from degradation of normal C1q during phagocytosis, culture-derived LMM-C1q appeared to be identical with LMM-C1q found in serum, as judged by sedimentation behaviour, subunit structure and recognition by poly- and mono-clonal antibodies raised against C1q. The presence of LMM-C1q in cytoplasmic organelles compatible with the Golgi apparatus and the inability to generate LMM-C1q by impeding hydroxylation and triple-helix formation of C1q further argues against degradation as its source. Monocyte cultures of homozygous probands from two families with complete functional C1q deficiency reflected the abnormalities in serum, i.e. absence of functional C1q, but increased levels of LMM-C1q. By contrast, secretion of C1q and LMM-C1q by cells from healthy individuals was clearly co-ordinate, indicating that LMM-C1q in serum may provide a unique marker of C1q synthesis in vivo.

Acquired C1-inhibitor deficiency associated with a lupus-like anticoagulant activity.

A patient with two attacks of glottis angioedema in a 15-day period without any apparent stimulus was studied. The complement profile of the patient revealed depletion of C4, C2, C1 inhibitor (C1INH) and C1q, with normal values of C3. Patient's offspring had a normal complement profile. Cytofluorographic analysis of the peripheral blood cells showed a marked increase of B cells. In the clotting study, a circulating lupus-like anticoagulant activity (LLA) was detected with a noticeable decrease of prothrombin time. Hepatosplenomegaly was confirmed by abdominal echography and CAT. From the liver biopsy it was concluded to be a lymphoproliferative process compatible with germinal center lymphoma. It is suggested that the neoplasm is probably the origin of the LLA and the cause of C1 activation, producing the biochemical defect of C1INH and the clinical symptoms of angioedema.

[Disorders in humoral defense: clinical aspects, diagnosis and therapy]. / Stoornissen in de humorale afweer: kliniek, diagnostiek en therapie.

Clinical and immunological findings of 5 patients with distinct defects in either humoral immunity or in the complement system are described. The syndromes presented comprise examples of type I dysimmunoglobulinaemia, X-linked agammaglobulinaemia (XLA), familial deficiency of complement factor C1q and a patient with a selective deficiency in the synthesis of antibodies against pneumococcal polysaccharides. The patients with a defect in humoral immunity all showed recurrent bacterial infections of the respiratory tract. The XLA-patient developed a dermatomyositis-like syndrome and ECHO-virus encephalitis. Prior to the development of a SLE-like syndrome the two siblings with C1q deficiency showed recurrent respiratory tract infections, most probably on basis of a defect in the clearance of immune complexes.

A homozygous point mutation results in a stop codon in the C1q B-chain of a C1q-deficient individual.

Southern blot analysis of the B-chain genes in one of eight C1q-deficient individuals revealed an abnormal banding pattern. The defect, which was homozygous, could be localized by restriction mapping to a single Taq I site within residue 150 in the coding region of the B-chain gene. DNA sequencing across the site revealed a stop codon that would cause premature termination of the protein product. No material corresponding to the A or C chains, or a truncated B chain, could be identified by antigenic analysis of the patient's serum, indicating that a complete B chain is required for secretion of a C1q molecule.

Underlying complement deficiency in patients with disseminated gonococcal infection.

The complement system was evaluated in 22 individuals with disseminated gonococcal infection. Three of the 22 patients exhibited a total serum complement activity that was greater than 2 SD below the normal mean. Of these three, one had a complete deficiency of C1r, a second patient had pre-existing systemic lupus erythematosus with low levels of C4, and the third had a C8 concentration that was 60% of normal. We conclude that the prevalence of inherited or acquired complement deficiency among patients with disseminated gonococcal infection exceeds that among the general population and is an important host factor predisposing to systemic infection with Neisseria gonorrhoeae.

Selective C1q deficiency in a patient with systemic lupus erythematosus.

We report a case of systemic lupus erythematosus with selective C1q deficiency. C1q deficiency had been presumed to be a non-hereditary disorder; however, the 10 reported cases in the world literature, and our case, suggest that C1q deficiency could also be an inherited disease.

Combined IgG2, IgG4 and IgA deficiency: low C1q concentrations and the presence of excess C1r and C1s in an adult patient with recurrent pneumococcal infections.

The complement (C) profile was investigated in an adult patient with combined IgG2, IgG4 and IgA deficiency and recurrent pneumococcal infections. The analysis revealed no gross impairment of the classic and alternative pathways of C activation. However, the concentrations of circulating C1q were persistently decreased, and the sera contained an excess of C1r-C1s complexes, resembling the C1 aberrations previously found in children with recurrent acute otitis media. The concentrations of C4 in the patient were persistently low. This could be ascribed to partial C4 deficiency with lack of C4A variants. The patient's IgG and IgM antibody responses to pneumococcal capsular polysaccharides and to other bacterial carbohydrate antigens were very poor. Interestingly, pneumococcal C-polysaccharide (CPS) could be detected in serum obtained during infection-free periods. Since CPS has been shown to bind C1q without causing C1 activation, the possibility was considered that the C1 aberrations in serum were due to circulating CPS. After administration of intramuscular gammaglobulin to the patient, the serum C1q levels were observed to return to normal.

Genetic deficiency of C4, C2 or C1q and lupus syndromes. Association with anti-Ro (SS-A) antibodies.

Sera from 15 patients with genetically determined complement component deficiencies were studied for the presence of antibodies to various nuclear antigens. One of three patients with C2 deficiency presented with systemic lupus erythematosus (SLE); all eight patients with C4 deficiency had either SLE or a lupus-like syndrome, and two of four patients with functional C1q deficiency had SLE. Five of nine complement deficiency patients with SLE studied had measurable antinuclear antibody titres, but only two had antibodies against native DNA. Precipitating antibodies against extractable nuclear antigens were found in sera from seven of the 11 complement deficient patients with SLE; one had only antibodies against antigens extracted from calf thymus (ECT), six patients (one with C2 deficiency, four with C4 deficiency and one with C1q deficiency) had anti-Ro (SS-A) antibodies with or without anti-ECT antibodies. The frequency of anti-Ro antibodies in the complement deficient population with SLE (55%) was significantly higher (P less than 0.02) than that of a control population of SLE patients without genetically determined complement deficiencies (27%).

Low molecular weight C1q in systemic lupus erythematosus.

In sera of patients suffering from an exacerbation of systemic lupus erythematosus (SLE), increased amounts of abnormal C1q were detected, contrasting with decreased or even undetectable levels of normal C1q in these sera. When analyzed immunochemically by double immunodiffusion, this low m.w. C1q (LMW-C1q) appeared to be identical with the defective C1q in serum of individuals with an inherited, homozygous inability to produce functional plasma C1q. These persons show a tendency to develop SLE-like syndromes. Like the genetically defective C1q, the abnormal C1q molecule in SLE sera was hemolytically inactive, did not incorporate in C1, was found in the supernatant of euglobulin-precipitated serum, and appeared in the break-through fraction of a cation-exchange column. Sucrose gradients and gel filtration analyses supported the putative identity of the molecules. SDS-PAGE and immunoblots revealed the presence of subunits that reacted with antibodies against C1q and confirmed the C1q-like nature of LMW-C1q. Low levels of LMW-C1q were also detected in serum and plasma of normal individuals. A radial immunodiffusion technique was used to measure LMW-C1q in the serum of 54 patients. Although these patients were not selected for parameters of disease activity, their levels of LMW-C1q were significantly higher than those of normal individuals and children with decreased C3 levels due to acute glomerulonephritis.

Atypical hypocomplementemic vasculitis syndrome in a child.

We report a patient who developed recurrent urticaria and angioedema at age 2 years, severe hypocomplementemic glomerulonephritis at 11 years, and end-stage renal disease at 14 years. His disease resembled the hypocomplementemic vasculitis syndrome but was atypical in its early age of presentation, severe hypocomplementemia, and progression to end-stage renal disease. Serum C1q levels were extremely low, and C4, C2, C3, and C5 levels were significantly reduced. Serum C1 inhibitor (C1INH) levels were slightly low, presumably from consumption. Circulating C1INH-C1r-C1s complexes were evidenced by reduced ratios of functional to antigenic C1INH and antigenic C1r to C1s. Family members had normal functional and antigenic levels of all complement components studied. The patient's serum, erythrocytes, platelets, and mononuclear cells did not activate complement when mixed with normal target serum. Absence of a circulating complement activator and the low serum C3 and C5 levels suggested the presence of a solid-phase complement activator, possibly related to renal or systemic vascular endothelium. As in patients with homozygous deficiencies of classical pathway components, a severe, prolonged, acquired C1q deficiency may have predisposed this patient to the development of glomerulonephritis.

Functional deficiency of complement factor D in a monozygous twin.

An adult twin with recurrent bacterial infections was found to have a partial functional deficiency of complement factor D. Full restoration of alternative pathway activity and zymosan- or cobra venom factor-induced consumption of C3 and B was found after reconstitution of patient's serum with purified D. Family studies revealed normal D levels in the mother, a brother and another sister. After gel filtration of patient's sera only little D activity could be detected in the fractions, and trypsin activation of the fractions also did not uncover detectable precursor D activity.

SLE like syndrome and functional deficiency of C1q in members of a large family.

Two sisters and a brother from one family are described whose sera were deficient in haemolytic complement function. This defect was restored by addition of purified C1q. In their sera, C1q like material was found, whereas C1r and C1s were normal or increased in concentration, as were the other complement components tested. All three had suffered from glomerulonephritis during childhood. A renal biopsy in the brother recently disclosed a membranous glomerulopathy stage 1; otherwise, he is apparently healthy. In both sisters, a systemic lupus erythematosus like disease became manifest at the age of 20 and 23, respectively, resulting in the death of one of them. In the serum of these three family members, the C1q like material was antigenically deficient compared with normal C1q and had, on sucrose gradient analysis, a molecular weight of approximately 65,000 daltons. It did not bind to C1r and C1s. Binding of the dysfunctional C1q to aggregated human gammaglobulin could be demonstrated. On double immunodiffusion analysis, the abnormal C1q was identical with reduced and alkylated C1q. The possible structure of the abnormal C1q molecule is discussed.

[Serum immunoglobulins and complement fractions in protein malnutrition]. / Immunoglobulines sériques et fractions du complément dans la dénutrition protidique.

Serum immunoglobulins and some complement components (C1q, C3c, C4, factor B, C9) have been evaluated in 99 malnourished patients. The sole abnormality which seems related to protein calorie malnutrition is a C1q decrease significantly correlated to serum albumin, thyroxin binding prealbumin and retinol binding protein. The immunoglobulins modifications seem to be related to pathological conditions associated with malnutrition (sepsis, liver diseases).

Inherited disorders of complement.

Isolated complement component deficiencies are uncommon. Deficiencies of all eleven components and two inhibitors of the classical pathway have been described. Complete absence of the components of the alternative pathway has not been described. The consequences of a single defect in complement are often predictable from an understanding of the biologic activities associated with activation of the complement system. Deficiency of C1 esterase inhibitor gives rise to the disease, hereditary angioedema; deficiency of the early components of the classical pathway are associated with lupus erythematosus; C3 and C3 inactivator deficiencies with pyogenic infections; C5 dysfunction with Leiner's disease; deficiencies of the terminal components with recurrent Neisseria bacteremia; and C9 deficiency with normal health. The complement system and its associated biologic activities are reviewed. The present knowledge of the inherited complement deficiencies and associated diseases, with particular emphasis on the dermatologic manifestations, genetics, and diagnosis, is summarized.