Greatly increased autoantibody production in myasthenia gravis by thymocyte suspensions prepared with proteolytic enzymes.

We have previously reported that cell suspensions prepared by mechanical dispersion of thymic tissue from myasthenia gravis (MG) patients spontaneously synthesise anti-acetyl-choline receptor autoantibodies (anti-AChR) in culture in many cases. We now find a 2-200-fold greater anti-AChR production if the cell suspensions are prepared with the proteolytic enzymes collagenase and dispase (THYC + D). This difference has been seen in seven of the first 10 cases tested. Using these enzymes, we now also find comparable anti-AChR synthesis by MG lymph node cells, confirming the presumed extra-thymic production of much of this autoantibody. The increased anti-AChR synthesis by THYC + D is not simply a mitogenic effect of the enzymes, but apparently depends on several distinct factors: (1) plasma cells are often isolated much more efficiently--particularly by dispase--than by mechanical dispersion of these tissues (or of 'normal' tonsil), and the same may also be true of specific B cells. (2) The greatly increased numbers of fibroblasts, macrophages and other adherent cell types exert 'feeder' effects which enhance anti-AChR and total IgG production non-specifically. (3) Specific antigen presenting cells (APC) may also be recovered more efficiently and selectively stimulate anti-AChR production by B memory cells. These results imply that APC, plasma cells, and perhaps also B memory cells are recovered from germinal centres much more efficiently by enzymic than by conventional dispersion, a conclusion that may be relevant to workers studying antibody forming and memory B cells in other systems or species.