Demonstration of complement-dependent and independent systems in immune inactivation of Mycoplasma meleagridis.

Abstract

The growth of Mycoplasma can be inhibited in the presence of specific immune serum. The inhibition is measured by the prevention of colony formation on solid growth medium where specific antiserum and the organism interact [1-3]. This process does not require complement [1, 3, 4], and the number of inhibited viable organisms is proportional to the amount of antiserum present [1, 2]. A similar phenomenon has been studied in liquid growth medium, and variable results have been reported. One form of inactivation of Mycoplasma by serum factors is characterized by a rapid decrease of viable organisms in liquid medium. The inactivation requires complement [5-9]. The rate of the reaction is independent of the number of organisms present but is dependent on the concentration of antibody and complement [5, 7]. Such inactivation has been shown to be completed within 60 min [5, 7] and is irreversible [7]. More recently, the mechanism of the complement-requiring inactivation of Mycoplasma pneumoniae has been elucidated. The organism is lysed due to damage of its surface membrane by antibody and complement [6]. This mechanism is similar to the complementdependent damage by antibody observed with erythrocytes [10], gram-negative bacteria [11], L-phase variants [12], mammalian cells [13], and viral particles [14-16]. Although less frequently observed, there appears to be another mechanism for inactivation of Mycoplasma by immune serum in liquid medium. This process may be characterized as compl ment-independent [3, 17, 18] and seems to be based on inhibition of multiplication of the organism [18]. The reaction seems to correspond to growth inhibition on agar medium. Thus, the above evidence indicates the existence of two different systems of in-vitro inactivation of Mycoplasma by specific antibody. However, the two inactivation systems have never been shown to occur in a single system. Instead, the ra her specific nature of the test methods used mig t lead one to believe that the two systems are not distinct from each other. This study will present data on complement-dependent and independent systems of inactivation operating simulta eously, but independently, in a broth-assay system with Mycoplasma meleagridis as the test organism.