Thrombocytopaenia, Thromboxane And Prostacyclin Production During The Forssman Reaction In The Guinea-Pig: Effect Of A Thromboxane Synthetase Inhibitor

Intra venous (iv) injection of Forssman antibody into the guinea-pig (GP) is known to result in a rapid antigen antibody reaction in the lungs leading to bronchospasm and thrombocytopaenia. Death as a result of Forssman shock has been shown to be complement and platelet dependentGroups of 5 Duncan-Hartley GP (350-400g) received either 0.2ml (sub lethal groups) or 0.6ml (lethal groups) of rabbit anti Forssman antiserum (RAFA) iv, then 5ml blood samples were collected via carotid artery cannula, into 0.5ml ice cold EDTA (lOOmM) and indomethacin (180μM) mixture at 0, 1, 3 and 5 min. post injection. The blood samples were rapidly centrifuged at 15,000g for 3 min, plasma removed and frozen at -20°C until assayed. The plasma was then assayed for TxB2 and 6-oxo-PGF1α using specific RIA’s. There was a marked TxB2 production during the thrombocytopaenia with a concomitant small increase in 6-oxo-PGF1α production.However, when groups of 5 GPs were dosed iv with 0, 1, 3 or 10 mg/kg of UK-37, 248, a potent and selective thromboxane synthetase inhibitor, 3 mins prior to 0.2ml of RAFA the resulting thrombocytopaenia was not inhibited at 0, 0.5, 1, 2, 5, 10 and 15 min post RAFA. Thus thromboxane production does not appear to be contributory to the Forssman induced thrombocytopaenia in the GP.

THE SUBUNITS IN RABBIT ANTI-FORSSMAN IGM ANTIBODY

Rabbit IgM anti-Forssman antibody was highly purified and the subunits obtained on reduction and alkylation were labeled radioactively and isolated by two different and unrelated methods. In both cases the subunits were found to have a molecular weight of about 90,000, based on their behavior on density gradient centrifugation and gel filtration, and evidence is given that they contained one light and one heavy chain. The subunits bound only weakly to sheep erythrocyte stroma, and only half could be shown to possess antigen specific sites. The data are consistent with the concept that each anti-Forssman IgM molecule has five effective binding sites, but it is uncertain whether the ineffectiveness of the remaining five H-L chain pairs is inherent in the structure of the IgM molecule or an artifact due to the isolation procedure. Intact IgM anti-Forssman antibody binds very firmly to structures containing multiple repeating antigen sites, and it appears that this is due to the presence of multiple binding sites on the molecule.