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Vielleicht hilft das (wegen der Nomenklatur)?

Let’s start by going back to basic high school biology. You may remember that white blood cells (a.k.a. leukocytes) are the components of blood that help the body fight infections and other diseases. White blood cells can be categorized as either granulocytes or mononuclear leukocytes. Mononuclear leukocytes are further sub-grouped into monocytes and lymphocytes.

Lymphocytes, found in the blood, tissues and lymphoid organs, attack antigens (foreign proteins) in different ways. The main lymphocyte sub-types are B-cells, T-cells and natural killer (NK) cells. B-cells make antibodies that are stimulated by infection or vaccination. T-cells and NK cells, on the other hand, are the cellular aggressors in the immune system and are our main focus in the discussion that follows.

Let’s pause a moment and introduce something you probably never learned about in high school biology class: CD markers. CD, which stands for “cluster designation”, is a glycoprotein molecule on the cell surface that acts as an identifying marker. Think of comparing cells as comparing people. Humans are made up of innumerable superficial identifying characteristics (such as hair color, eye color, etc.) and so are cells. Cells probably have thousands of different identifying markers, or CDs, expressed on their surfaces, but 200 or so have been recognized and named so far.

Each different marker (or CD) on a cell is named with a number, which signifies nothing more than the order in which the CD was discovered. On any given cell there are many different cluster designation markers (CDs), giving each cell its unique appearance and function but also linking certain cells by their similarities (like grouping all people with brown hair or all people with blue eyes). Cells that have a certain kind of CD present on their surface are denoted as + for that CD type (e.g., a cell with CD57 markers on its surface is CD57+).