I often get a cold, because I have weak immune system.

我经常感冒，因为我抵抗力差。

youdao

An experimental therapy uses a person's weak immune system to fight deadly blood cancers.

一种实验疗法利用人体虚弱的免疫系统对抗致命的白血病。

youdao

The following acupressure points are effective for dealing with a condition that may be caused by a weak immune system.

下面的穴位是有效的免疫系统弱的处理与一个可能的条件所致。

youdao

However, patients with a weak immune system may not be able to do this - at which point the tuberculosis bacteria starts to spread in the lung.

BBC: TB link to ethnic minority poverty

Tuberculosis can lie dormant in a person for years and then strike when the immune system is weak.

BBC: NEWS | Health | Breathalyser detects tuberculosis

Who knows whether the symptoms are just being noticed once all the activities wind down or whether a child is simply fatigued enough that their immune system becomes a little weak.

CNN: Why do kids always get fevers on Sunday nights?