The resistance to human plasma of Trypanosoma brucei, T. rhodesiense and T. gambiense: III. Clones of two plasma-resistant strains.

Tests for resistance to human plasma were made on six clones of a stabilate of Trypanosoma rhodesiense (LUMP 10) which was calculated to contain about 3,000 resistant trypanosomes per million. Two of the clones were not resistant and four were only subresistant. Tests were also made on 12 lines (clones) of a stabilate of polymorphic trypanosomes isolated from tsetse flies. One of them, ETAT 10, had infected a laboratory worker and was found to be fully resistant to human plasma; the other lines showed only low or moderate resistance. Resistance of a strain to human plasma often depends upon a small minority of resistant trypanosomes. Strains of polymorphic trypanosomes may be classified as fully resistant, moderately resistant, subresistant, or sensitive to human plasma, if they contain respectively, all, some (e.g. one per hundred), very few (e.g. one per million) or no individuals which are resistant.