by different isolates produced different amounts of il 10 and il 12 whose ratios correlated with the levels of ifn u03b3 and in vivo protection as shown in table 8 nthi isolates b3 b6 with a low il 10 il 12 ratio were better stimulators of a th1 response characterised by maximal production of ifn u03b3 and decreased colonisation of bacteria in the airways of mice orally immunised with killed vaccine isolates compared with controls conversely isolates b4 b10 and b14 with high il 10 il 12 ratios correlated with lower production of ifn u03b3 and higher levels of colonisation this was also true for s aureus isolates where high levels of ifn u03b3 correlated with low il 10 il 12 ratios and low rates of colonisation table 9 taken together the results show that an optimal isolate of bacteria can be selected as a candidate vaccine on the basis of low il 10 il 12 ratio and high ifn u03b3 and an enhanced protection in vivo thus on the basis of these results an optimal isolate would be associated with a cut off value of il 10 il 12 ratio of say lt 15 and high production of ifn u03b3 786 pg ml for nthi and gt 500 pg ml for s aureus for all healthy subjects tested minimum of 3 subjects compared to table 6 in example 2 nthi 164 expressed comparable levels.