Macrophage Inhibition Factor

1. Peritoneal exudates from antigen-sensitized guinea pigs, containing both macrophages and lymphocytes are placed into capillary tubes. If the sensitizing antigen is not added, the macrophages will migrate out of the tube forming that fuzzy, mushroom-like head shown in the pictures. Although the lymphocytes in the tube with the macrophages are committed to one antigen (sensitized), they will not produce lymphokines until the second or subsequent contact with the same antigen.
   
2. The migration is inhibited when antigen to which the lymphocytes are sensitized is added to the cell mixture. Macrophage Inhibition Factor (Interferon) is released by sensitized lymphocytes in the capillary tubes, responding to the presence of the sensitizing antigen. It is the MIF that inhibits the macrophage migration not the antigen.
   
3. Look at the photos. The top row shows the results when macrophages and lymphocytes are collected from normal (unimmunized) guinea pigs. The macrophages migrate freely with or without the antigens because the lymphocytes are "seeing" the antigen for the first time; no MIF is being produced. In addition, these controls show that any response by the macrophages in the other tubes is independent of the nature of the antigen.
   
4. The inhibition of migration of macrophages from the tubes is only seen in that tube which has both the ovalbumin sensitized lymphocytes and the ovalbumin antigen, or the tube with both toxoid sensitized lymphocytes and toxoid antigen.

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