I have grown Hela cells in DMEM media for 8days continuously, but volume of media was only 3 ml with 10% FCS and they grown nicely. So I can suggest you to try DMEM with 10 % FCS and take more volume as you need. Also keep adding FCS in that in a scheduled time period to keep your cells in a nutritious environment.

I think rpmi is much better for blood cells

To absorb the IgG from you media, you can try use G protein. This a technique used to absorb the IgG from sera in ELISA.

I am not directly familiar with this test as you are peroforming it but RBCs are the "shuttle" to remove immune complexes by CR! receptors on the RBCs. If HeLa cells have CR1 receptors, you may need to add plasma containing complement (check Quidel). The deposition of complement onto IgGs should allow for HeLa cell binding through the CR1 receptors if present. Raji cells are used for immune complex detection (have CR1). Can these cells be used? Good luck-

This is "old school" immunology. I don't think any of the proposed answers is exactly what you are looking for, as adsorb means to bind or coat the surface of the RBC rather than absorb which would be to remove Ig from sera or media. If I understand what you want, you are looking to have a permanently sensitized RBC pool from which you can do the Coombs Test, or really a hemagglutination or hemolysis test. We used to do this with sheep RBC and then store the RBC in Alsever's solution at 4C but they would only last a couple weeks. You would know when they were going bad because the vial/tube would begin auto-hemolysis. The specifics of the amount of Ig to incubate with the RBC pool is far beyond my memory and there may be companies (Sigma perhaps) that sell sensitized RBC,however they may only sell sheep RBC. Good Luck.

One easy way to have a positive control could be Rh+ RBC treated with antiserum anti-D. The specific immunoglobulin will be adsorbed to RBC in this way. As Dr. Laning said, we used Alsever solution to maintain sheep RBCi at 4ºC, in the past, but they lasted only 1-2 weeks maximum. I add a link that could help you with the media to be used:

http://www.bloodindex.org/blood_anticoagulation_preservation.php

Good luck.