SUMMARY 



Immunology. The effect of cold on circulating antibody was dis- 

 cussed by Dr. Campbell. Two factors which he pointed out that should 

 be kept in mind were 1) the effects of cold on antibody production and 

 antigen breakdown, and 2) the effects of cold on antibody removal 

 from the circulating blood. 



In general, the participants reported a decrease in circulating an- 

 tibody in chilled animals. However, Dr. Northey found little difference. 



Cold and microbialfloraof host. The effect of maintaining mice at 

 22° C to 23° C on the invasion of the blood stream and peritoneal 

 cavity, as reported by Dr. Tunevall, emphasizes how little we know 

 as to the permeability or impermeability of the gut to the passage of 

 macromolecules or microorganisms. This permeability might not be 

 of significance except that as Dr. Tunevall reports, clearance of 

 bacteria from the blood stream is also impaired in the hypothermic 

 animal. A basic explanation of both findings is in order. 



Another mechanism by which cold may alter host microbial flora 

 is suggested by Dr .Schmidt's report onthe intestinal flora of squir- 

 rels as affected by hibernation. He found a sharp increase in psych- 

 rophilic bacteria.Such a change in intestinal flora, induced by hypo- 

 th'ermia,could be associated with changes in available vitamin K pro- 

 duced by the normal intestinal flora and more significantly, with an 

 increase or decrease of antimicrobial agents produced by intestinal 

 bacteria. 



SUMMARY 



In conclusion, it is safe to say that the final blue print showing 

 the anatomical physiological biochemical and immunological mech- 

 anisms by which exposure to cold alters host resistance to infection 

 will not be simple. But it will be a workable paper and will suggest 

 practical ways of increasing host resistance. 



453 



