Generation of chemotactic activity in normal guinea pig serum by treatment with acid

Chemotactic activity was generated in normal guinea pig serum following titration of the pH to 4 by the addition of hydrochloric acid. The process was time and temperature dependent. The chemotactic material was stable when kept at pH 4, but decayed within one or two days when the pH was raised to neutrality. Fractionation of the acid-treated serum by Sephacryl S-200 gel filtration revealed two peaks of activity, one eluting with molecules larger than bovine serum albumin, the other in the 13,000 MW range. After heating the serum at 56 degrees C for 60 min no chemotactic activity could be generated by acid, while EDTA, EGTA, hydrazine and the enzyme inhibitors benzamidine, EACA, PMSF, and pepstatin, added to the serum prior to the addition of acid, had no effect. The results suggest that chemotactic factors, remarkably similar to the products of complement activation, could be generated in guinea pig serum by a mechanism differing from the classical or the alternative complement activation pathways.