Studies of host responses during experimental gingivitis in humans. II. Changes in acute phase reactants, serum immunoglobulins and complement during the development of gingival inflammation.

To determine if the early accumulation of plaque in experimental gingivitis is associated with systemic alterations in acute phase serum proteins, immunoglobulins and complement, serial serum specimens were obtained from experimental subjects and matched controls. Therre were no singnificant changes in acute phase reactants (C-reactive protein, transferrin, alpha-1-antitrypsin) or IgG, IgA or IgM. Total hemolytic complement (CH50) and C4 quantitative levels rose significantly in the experimental subjects 21 days after discontinuing oral hygiene, but not in the controls. There were no significant changes in C3 or Factor B levels in either group. Thus, there was no evidence of gross activation of the complement system by either pathway (e.g. consumptive depletion). On the other hand, functional analysis of the sera for spontaneous, complement derived, neutrophil chemotactic activity (SCA) revealed the following: (1) significant elevation in SCA occurred in the experimental subjects 3 and 21 days after discontinuing oral hygiene (compared to the Day 0 baseline value) but did not occur in the controls; (2) the elevated SCA was C5-dependent; and (3) elevated serum SCA at days 3 and 21 was correlated with the enhancement of plaque mediated lysosomal release from polymorphonuclear leukocytes, incubated with aliquots of these sera. The data suggest that subtle degrees of systemic complement activation occur in experimental gingivitis but are only detected by sensitive, functional assays.