Figure 9.  Immature and mature NK cells express mRNA for each of the component chains of IL15 and IL2 receptors

The failure of NK cells to respond efficiently to low concentrations of IL2 or IL15 suggests that they might not

express the IL2Ra and IL15Ra chains that are required for formation of high affinity receptors.  This possibility

was tested by examining highly purified NK cells for the presence of IL2Ra and IL15Ra mRNA.

A

B

C

D

E

F

G

H

I

IL15Ra Isoform 1

IL2Ra

IL2/IL15Rb

gc

RNA was prepared from equal numbers of:

A.  CTLL2 cells

B.  ConA activated CD4 T cell blasts

C.  ConA activated CD8 T cell blasts

D.  Water

E.  Purified normal adult NK cells grown for 7 days in 20nM IL2

F.  Immature NK cells obtained by growing E14 thymocytes for 3 days in IL4 + PMA then for 3 days in IL2

G/H.  Two NK cell clones obtained following 7 days culture in 20nM IL2 of individual E14 thymocytes

that had been grown initially for 2 days in IL4 + PMA.

Conclusions

1.  NK cells, like T cells, express mRNA for the IL2/IL15Rb and gc chains that form the low affinity receptors

for IL2 and IL15.

2.  Contrary to the widely held and frequently stated view, both immature and mature murine NK cells express

easily detectable mRNA for IL2Ra chains.  That this is not an artefact caused by small numbers of contaminating

T cells [or other cells] is proven by the presence of IL2Ra mRNA in cultured RAG knockout NK cells and in

NK cell clones derived from single immature progenitors that by staining were 100% NK1.1+ CD3 - cells.

3.  Immature and mature NK cells also express mRNA for Isoform 1 of the IL15Ra chain that contains the

complete extracellular region and forms the high affinity IL15 receptor.

4.  However, IL15Ra mRNA exists in multiple forms due to extensive alternate splicing of primary transcripts

5.  Alternately spliced isoforms were more prevalent in NK cells than in T cells.