Immunological distances

A number of immunological techniques have been used in comparative studies.8,9 The most important of these is microcomplement fixation (MC F), a quantitative technique that has played a key role in many classic studies of molecular evolution and molecular systematics. By selecting proteins with different rates of evolution, a broad range of divergences can be examined. The cost of the technique is moderate, but biochemical expertise is required and the labor involved is substantial. Protein must be purified from some or all taxa for antibody production, and, for those taxa, a sizable tissue or serum sample is needed. Antibody production itself is usually done in rabbits, so an animal care facility must be available. Like isozyme electrophoresis, the large body of immunological distance data already available ensures the continued value of this technique for certain investigations. 

Information Content of Immunological Distances By Ellen M. Prager and Allan C. Wilson ... 

To assess the certainty with which the extent of difference in amino acid sequence can be inferred from immunological distance, we have estimated prediction intervals for five kinds of monomeric proteins. These estimates are made possible by the extensive calibration work done in our laboratory on proteins of known amino acid sequence. This chapter then uses prediction intervals to test the robustness of hypotheses about phene-tic relationships among monomeric proteins of mammals, frogs, and birds. The probabilities of arriving at various conclusions by chance range from 1 in 20 to 1 in 10 billion. 

Fig. 1. Confidence limits and prediction intervals for immunological comparisons of five proteins. For each protein the heavy central line is the regression line through the origin relating immunological distance in the microcomplement fixation test to percent difference in amino acid sequence, and the shaded region portrays the 95% confidence limits for that line. The outer two lines in each graph define the boundaries of the intervals for one prediction made at the 90% level of confidence.

Probability That Two Immunological Distances Represent Same Extent of Sequence Difference An Albumin Example0... 

Consider first the immunological distances of 6 and 22 for albumin. As explained in Table II, whichever method of assessing probability (1 or 2) is used, these two albumin distances are not statistically significantly different. There is an 11-19% (average, 15%) probability that 6 and 22 could be obtained by chance even if bear albumin were equally distinct in amino acid sequence from the two panda albumins. 

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