We live in a sea of infectious agents, and we have evolved several mechanisms for protecting ourselves against those that are potentially pathogenic.

In a general sense, we can think of our defenses as consisting of three types.

Learning Objectives

After successfully completing this learning module, the student will be able to:

>  Macrophages and dendritic cells

> Neutrophils

> Eosinophils and basophils

> Natural killer cells

> Helper T-lymphocytes (helper T-cells)

> Cytotoxic T-lymphocytes (cytotoxic T-cells)

> Regulatory T-cells (Treg)

> B-lymphocytes (B-cells) and plasma cells