Human serum mannose binding protein (MBP): development of an enzyme-linked immunosorbent assay (ELISA) and determination of levels in serum from 1085 normal Japanese and in some body fluids.

We developed an enzyme-linked immunosorbent assay (ELISA) for human serum mannose binding protein (MBP), an animal lectin known to function as opsonin and complement activator. A total of 1085 normal Japanese sera from individuals ranging in age from 3 to 100 years old and additional body fluids were measured for the MBP level. Individual serum MBP levels ranged from 0.07 to 6.40 micrograms/ml with a frequency distribution profile of the log-normal type. Arithmetic mean +/- standard deviation (M +/- SD) of serum MBP as a whole was 1.72 +/- 1.15 micrograms/ml, whereas those of cerebrospinal fluid and urine were 1/100 and 1/1000 of serum levels, respectively. When the M +/- SD of serum MBP was calculated for each age group (10-year intervals) and compared, the value declined from age group of 3-9 years old (2.42 +/- 1.31 micrograms/ml) to that of 20-29 years old (1.72 +/- 1.03 micrograms/ml), and thereafter it remained almost constant. Comparing the frequency distribution profile among each group, that of young group revealed a distinct bimodal pattern, one peak at around 1 micrograms/ml and the other at 3 micrograms/ml. The latter peak was gradually depressed with advance of age and finally a typical log-normal type appeared after the age of 30. There was a high age dependency in serum MBP level as well as in distribution profile. It should be stressed that care should be taken with age in the evaluation of MBP level.