体液免疫，即通过B细胞产生抗体来达到保护目的的免疫机制，属于特异性免疫。

体液免疫作用机制如下：当抗原(细菌、病毒、外来物)第一次感染人体时，会被非特异性免疫的细胞所吞噬、清除，而其中一部分细胞特称抗原呈现细胞（APC）。其中，在刺激B细胞方面主要是树状细胞。抗原呈现细胞除了能吞噬、分解抗原，还能将分解的的碎片（肽链）呈现给B细胞，使之活化、分裂。并经株落选择筛选出对抗原最具亲和力的IgM型抗体。抗体的变异区能与抗原产生专一性的结合，阻止它感染正常细胞，并用另一端的Fc区与巨噬细胞结合，使巨噬细胞吞噬抗原，达到消灭细菌的目的。

Humoral immunity, also called the antibody-mediated beta cellularis immune system, is the aspect of immunity that is mediated by macromolecules (as opposed to cells) found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides. Humoral immunity is so named because it involves substances found in the humours, or body fluids.