374 IMMUNOGENETICS 



(enhancement). Techniques for these essentially immunologic systems, of considerable 

 genetic interest, will not be elaborated here; references to most of the current pro- 

 cedures will be found in an earlier review by Owen. 986 



Bone-marrow transplantation. — There is a great deal of activity currently in the area 

 of hematopoietic transplants into irradiated adult mammals, especially mice. 393 The 

 genetically controlled incompatibilities between host and graft in this system are of 

 particular interest and importance. Brief mention will be made here of the essential 

 and most-used techniques. 



Donor mice are generally killed by bleeding them to death, often by decapitation; 

 there is reason to believe 451 that exsanguination of the donor may reduce the number 

 of a type of cell in peripheral blood that may have an unfavorable effect on the host 

 into which the bone marrow is to be injected. The mice are pinned or taped securely 

 on a board and each femur is exposed, dissected out, and transferred to a petri dish 

 where the femurs are scraped free of adhering tissue and rinsed with Locke's solution. 

 Generally, the dosage of bone marrow to be used will approximate one or two femurs 

 per recipient. Both ends of the femur are cut off with a scissors, and the marrow plug 

 is forced out, using Locke's or Tyrode's solution in small quantity to flush out the 

 marrow canal with a 22-gauge needle and a 2 ml. syringe. The marrow is then 

 suspended evenly by filling and emptying the syringe, forcing the suspension through 

 the needle several times, and the nucleated cell count is taken in a hemocytometer 

 using crystal violet in 1 per cent acetic acid as a stain. The suspension is adjusted so 

 that it will contain the desired count of nucleated cells per \ ml., the quantity injected 

 intravenously into each recipient. 



Radiation conditions for the recipients are specified in publications in the field. 393 

 Several techniques have been applied to follow the course of repopulation of the 

 erythropoietic tissues. 983 



Embryonal hematopoietic tissue, especially embryonic liver, is often substituted 

 for adult bone marrow. It seems to have some advantages, in terms of its lesser 

 tendency to produce a delayed incompatibility reaction and in terms of its ability to 

 transplant, at least in genetically anemic recipient mice, even without irradiation of the 

 host unless strong histocompatibility barriers are present. 1099 



The main genetic tools for studies of transplant incompatibility have been the in- 

 bred lines of mice, their hybrids and segregating F 2 and backcross generations. 983 

 The development of coisogenic lines differing only at specified loci affecting histo- 

 compatibility, by George Snell at the Jackson Laboratory, has provided the most 

 precise information about immunogenetics in this important area, and the most useful 

 materials for its advancement. 



DISCUSSION 



Dr. Burdette: Dr. Henry J. Winn of the Jackson Laboratory will open the 

 discussion of Dr. Owen's paper. 



