Figure 3.  NK cells developing in vitro from early thymic progenitors also progressively acquire CD94 molecules but with different kinetics than Ly49 molecules
		Fresh E14 thymocytes contain a small but easily detectable subpopulation
		of CD94+ cells.  As in the case of adult splenic NK cells [see below], about
		70% are CD94hi and about 30% CD94lo
		In contrast to the situation for Ly49 molecules, CD94+ cells, especially
		CD94lo cells, develop during the initial culture period in IL4+PMA
		The development of CD94 cells continues in secondary IL2-containing
		cultures.  By 3 days, about 25% of cells are CD94hi and about 40% CD94lo,
		but many CD94- cells are still present.
		By 6 days after transfer to IL2 essentially all cells are CD94+, about 30%
		being CD94hi and 70% CD94lo.  Note that, in contrast to the situation for
		Ly49 molecules, the level of expression of CD94 on CD94hi cells is
		constant throughout development.
		By 16 days the proportion of CD94hi cells has reached maximal levels
		at about 30-40%
		Thereafter, in further contrast to the situation of Ly49 molecules, the
		proportion of CD94+ cells frequently declines.  In this experiment the
		proportion of CD94hi cells declined to <5% by day 40.
		Control staining of cultured adult splenic NK cells with anti-CD94.
		Note that all such cells are CD94+, about 70% being CD94hi
Conclusions
1.  Throughout development, CD94 is expressed on NK cells at two clearly different levels
2.  In contrast to the situation for the Ly49 molecules recognized by 4D12:
a) an easily measurable proportion [3-4%] of fresh E14 thymocytes express CD94
b) up to 30% of these cells acquire at least low levels of CD94 during culture for two
days in IL4+PMA
c) by 6 days of secondary culture in the presence of IL2 essentially all cells have
acquired at least low levels of CD94
d) after 10-14 days of culture with IL2 the acquisition of CD94 has reached maximal levels
e) throughout development the level of expression of CD94 on CD94hi cells is constant
f) thereafter there is usually a progressive decline in CD94 expression on NK cells that
develop in vitro, and most long-term lines and clones of such cells are CD94-