Interaction of 1.5‐MHz ultrasound with human lymphocyte cultures

Abstract

Lymphocytes constitute some 30% of the white cell population of human blood and any medical exposure to ultrasound will involve irradiation of this important cell group. Lymphocyte death, as monitored by pyknosis, has been found to follow almost immediately on exposure of cultures to 1.5‐MHz continuous wave ultrasound, at power levels which leave the cells intact, and which are within the usual therapy range. An intensity threshold for the effect exists at ∼1.l W/cm2, and it is shown how both the number and induced pyknosis rate of the affected cells are modified by the parameters of the exposure. The response to pulsed ultrasound is very different, with a 15−20‐h delay in the measurable consequences of the sonication. A remarkable result is that the course of the ultrasound action is strongly modified in the presence of certain drugs. Experiments relating to the sonic impairment of lymphocyte function are also discussed, and some preliminary results reported. Some evidence is presented to suggest that cavitation is an important interaction mechanism, but some difficulties with this interpretation are discussed.