The serum levels of
immunoglobulins G, A and M and of the four subclasses of
IgG have been measured in 54 patients with the
nephrotic syndrome; 27 had
minimal change disease (MCD), 9
membranous glomerulopathy (MGN), 5
focal glomerulosclerosis (FGS), 5 proliferative
glomerulonephritis (PGN) and 8 miscellaneous forms of
nephrotic syndrome (Table 1). Low levels of
IgG and A, previously described in MCD, were found in all histological diagnoses; only about half the cases of MCD showed a high
IgM. Measurement of the subclasses
IgG 1-4 showed all to be depressed. Proportionately, however, the
IgG2 was most affected (8.8% total
IgG, cf 18.3% controls). Urinary
protein loss, either total or
IgG, only partially correlated with
IgG suppression, while
IgG2 in the urine usually comprised an even lower proportion of total
IgG than in serum. The
polyethylene glycol (PEG) 6,000 precipitate from serum at 4% concentration was also examined for
IgG and subclasses in MCD (27 cases), MGN (9 cases) and PGN (3 cases). Raised levels above those of 14 normal controls were found in nearly all cases of MCD, even in remission, but in no cases of MGN. In MCD no
IgG4 was found in any of the precipitates, while
IgG2 was proportionately raised (22% of total) in the precipitate as compared with whole serum (8.8%). Serial studies on 9 adults (3 MCD, 3 MGN, 1 FGS, 1 PGN, 1
IgA nephropathy) showed only that the low levels of
IgG and subclasses were associated with relapses and reverted toward normal in remission.