Macrophage Chemotactic Factor

1. When lymphocytes that are sensitized to a specific antigen (in this case histoplasmin) are incubated with that antigen, they produce a soluble macrophage chemotactic facotr. This factor diffuses away from the lymphocytes, forming a concentration gradient which directs the macrophages to the site.
2. Look at the photo. Three wells were cut in an agar covered slide. Normal macrophages were placed in the center well.
3. Histoplasmin sensitized lymphocytes were mixed with histoplasmin. The liquid (no cells) from this mixture was placed in the right well.
4. Normal (unsensitized) lymphocytes were mixed with histoplasmin. The liquid (no cells) from this mixture was placed in the left well.
5. Migration of macrophages outward from the center well was accelerated only in the direction of the gradient of MCF originating from the top well.
6. The chemostatic index is the ratio of distance A to distance B. In the example shown, the index is 2.0.

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