FURTHER CHARACTERIZATION OF THE IMMUNE-RESPONSE OF THE KOALA

Sensitive enzyme immunoassays (EIA) were developed to monitor antibody (Ab) production in the koala, in response to both soluble and particu late antigens (Ag). When compared with a eutherian mammal, the rabbit, both the dynamics and kinetics of Ab production in the koala were fou nd to be severely retarded. In vitro, Ag specific lymphocyte prolifera tive responses were demonstrated for the first time in this animal by sensitising koalas in vivo with Bacillus Calmet-Guerin (BCG), with the level and timing of this cell mediated immune (CMI) response comparab le with those seen in non-metatherian mammals. Levels of circulating B lymphocytes were examined in an attempt to clarify the retarded humor al responses to foreign Ags. In addition, peripheral mononuclear cells (PMC) from koalas, were examined for their reactivity to a range of m onoclonal Abs and lectins in an attempt to characterise these cells fu rther. The lectins examined, demonstrated an all or none reactivity wi th koala lymphocytes and were therefore considered unsuitable as marke rs for identifying lymphoid subsets in this animal. A monoclonal Ab di rected at class II MHC Ags in the mouse, demonstrated cross reactivity with a high percentage of all koala monocytes tested. Using this Ab t o probe CMI responses in vitro, it is concluded that immune interactio ns required for such responses in the koala parallel those seen in oth er mammals.