Here are a few description options for a WordPress post_tag with the title “白血球” (White Blood Cells) in Traditional Chinese, varying in length and focus:

**Option 1: Concise & Informative**

> 白血球 (Bái xuè qiú): 免疫系統中的重要組成部分，負責保護身體免受感染和疾病侵襲。 了解白血球的功能和重要性。
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> *Translation:* White Blood Cells: An essential component of the immune system, responsible for protecting the body from infections and diseases. Learn about the functions and importance of white blood cells.

**Option 2: Slightly More Descriptive**

> 白血球 (Bái xuè qiú): 人體免疫系統中的關鍵細胞，參與抗菌、抗病毒等防禦機制。 包含不同類型的白血球，例如淋巴細胞、嗜中性球等。
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> *Translation:* White Blood Cells: Key cells in the human immune system, involved in defense mechanisms against bacteria, viruses, etc. Includes different types of white blood cells, such as lymphocytes, neutrophils, etc.

**Option 3: Emphasizing Health & Wellness**

> 白血球 (Bái xuè qiú): 守护健康的重要角色。了解白血球的功能，以及如何通过健康的生活方式支持白血球的生产和活跃度。
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> *Translation:* White Blood Cells: An important role in safeguarding health. Learn about the functions of white blood cells and how to support their production and activity through a healthy lifestyle.

**Option 4: Technical but Clear for a Targeted Audience (e.g., Medical/Science)**

> 白血球 (Bái xuè qiú): 指的是存在于血液中的免疫細胞，能够识别并清除入侵身體的病原體。 包括粒细胞、淋巴细胞和單核細胞。
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> *Translation:* White Blood Cells: Refers to the immune cells present in blood, capable of recognizing and eliminating pathogens that invade the body. Includes granulocytes, lymphocytes, and monocytes.

**Which Option to Choose:**

The best option depends on the overall tone and content of your website:

* **Option 1:** Good for general health information. Concise and easy to understand.
* **Option 2:** Suitable for a slightly more detailed explanation, perfect for health-related websites.
* **Option 3:** Emphasizes health and wellness, great for content focused on healthy living.
* **Option 4:** Appropriate for scientific or medical-focused websites.

Remember to choose the description that best aligns with the other content on your site and consider your target audience. You can enter these descriptions directly into the WordPress post_tag description field when editing the tag.