Gamma G globulin subgroup composition of the glomerular deposits in human renal diseases

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Abstract

36 renal biopsies from patients with nephritis were studied for glomerular localization of the heavy chain subgroups of immunoglobulin G (IgG or γG). The deposition pattern of these subgroups was selective and did not reflect the normal serum concentration of these proteins. γG2, which comprises 18% of normal serum γG, was the predominant or unique subgroup deposited in five cases of lupus nephritis and four biopsies with other forms of nephritis associated with granular γG deposits. γG3, which normally makes up only 8% of the serum γG, was the dominant subgroup seen in one biopsy of lobular glomerulonephritis. Patients with linear γG deposits generally had a selective absence of γG3 and often had large amounts of γG4 (normally 3% of the serum γG) deposited. The deposition of complement components C1q, C4, and C3 was variable. One biopsy had only γG2 and no complement components in the deposits and had no neutrophile leukocyte infiltration. This latter observation correlates well with the poor ability of γG2 to fix complement in vitro. Similarly, deposits containing large amounts of γG4, which does not fix complement, also tended to have less inflammatory infiltrate than deposits devoid of this subgroup. The selective deposition of monotypic or restricted γG subgroups on the glomerulus supports the likelihood that the γG represents antibody. The nature of the subgroup involved in the deposit may represent one variable in the determination of the inflammatory and morphological picture that evolves in human glomerulonephritis.

Authors

Edmund J. Lewis, George J. Busch, Peter H. Schur