1、im- "not, opposite of" => "这里引申为：free from, exempt from" + muno- + deficiency.2、字面含义：free from or exempt from public service or duty, exempt from service or obligation. 也就是不用做公共服务，免除了公共服务。3、按咱们古代的说法：就是不用服劳役。由此引申为：豁免、免除、免疫。
实用例句
1. human immunodeficiency virus or HIV
人体免疫缺陷病毒，即HIV
来自《权威词典》
2. These conclusions have emerged from observations of persons exhibiting different states of immunodeficiency.
这些结论是从观察人的各种免疫缺陷症状得出的.
来自辞典例句
3. Objective: To review the pathogenic mechanism of acquired immunodeficiency syndrome ( AIDS ).