XXXX , BCG, modulation of murine antibody responses: influence of dose and degree of aggregation of live or dead organisms.

@entity308 @entity19 @entity653 @entity4558 @entity381 @entity2497
Mycobacteria have the ability to enhance or depress immune responses. This paper describes experiments designed to investigate the parameters determining the direction of modulation. It has been shown previously that 10(8) liver @entity2497 BCG depress the ability of @entity19 spleen cells to produce a primary antibody response in vitro to SRBC 2-3 weeks after i.v. injection, whereas the same number of dead organisms enhance this response. Using the same growth medium for the BCG (Glaxo @entity653 -free medium), we now find that decreasing the BCG dose to @entity19 from 10(8) to 10 (6) liver organisms results in enhanced responses and increasing the dose to more than 10(8) dead organisms results in @entity308 responses. It thus appears that bacterial load is the important factor determining whether @entity308 or enhancement of the primary antibody response will occur, rather than the viability of the organisms per se. However, when the BCG was grown in Middlebrook 7H9 broth, doses as high as 4 X 10(9) dead BCG/ @entity19 failed to depress although @entity308 responses were found if sufficient live organisms (7 X 10(8)) were injected. In view of the known growth characteristics of BCG in these 2 bacteriological media, it is suggested that the degree of aggregation of the injected suspension may also be of importance in determining whether or not @entity308 will occur. A comparison of the effects of BCG injected untreated or after dispersion of bacterial aggregates supports this idea. Some degree of @entity381 was always found in @entity19 with @entity308 @entity4558 responses but a large spleen did not necessarily yield cell suspensions with @entity308 responses.
