COMPONENTS OF BIOLOGICAL VARIATION IN PLASMA HAPTOGLOBIN - RELATIONSHIPS TO PLASMA-FIBRINOGEN AND IMMUNE VARIABLES, INCLUDING INTERLEUKIN-6AND ITS RECEPTOR

We investigated the components of biological variation, including seas onality, in plasma haptoglobin (Hp) levels and the relationships betwe en plasma Hp and interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6), sIL-2R, fibrinogen (Fb) and absolute number of peripheral blood mononu clear cells, such as leukocytes, neutrophils, monocytes, lymphocytes, CD4(+), CD8(+), CD25(+) T cells and CD20(+) B cells. Monthly blood sam ples were taken from 26 normal volunteers during one calendar year. Th e estimated inter- and intra-individual C.V. values for plasma Hp were 27.9% and 20.0%, respectively; the index of individuality was 0.72. N o significant seasonal rhythms could be detected in plasma Hp levels. The yearly mean values in plasma Hp were significantly and positively related to those in plasma Fb, absolute number of leukocytes, neutroph ils, CD4(+) T cells and the CD4(+)/CD8(+) T cell ratio. 49.0% of the v ariance in the yearly mean values of plasma Hp could be explained by v ariances in serum IL-6 and number of CD4(+) (positively related) and C D8(+) (negatively related) T cells. There were significant and positiv e time relationships between plasma Hp, on the one hand, and plasma Fb , sIL-6R, sIL-2R and number of leukocytes, neutrophils and monocytes, on the other. A smaller part of the within-subject variability in plas ma Hp (i.e. 6.0%) could be explained by serum sIL-6R and sIL-2R. It is concluded that there are (1) important between-subject differences in the homeostatic setpoints of plasma Hp, which are related to those in plasma Fb and in immune status and (2) significant within-subject, ti me relationships between plasma Hp and indicators of immune activation and plasma Fb.