[3.1] The invention is concerned with blood processing systems, in particular with a system for the separation of whole blood on the one hand (see claim 1), and a method for collecting diluted mononuclear cells obtained from the separation of whole blood (see claim 4).
[3.2] D1 discloses a system and a method for the centrifugal processing of a liquid, for example whole blood, to collect species which are sparse within the liquid, for example mononuclear cells […].
[3.3] The board regards D1 as representing the closest prior art, as did the appellant.
[3.4] Starting from D1, the technical problem underlying the application may be defined as the provision of a system and a method for the separation of whole blood leading to a product of mononuclear cells which remains pure after dilution with plasma […].
[3.5] As the solution to this technical problem, the application proposes a blood processing system according to claim 1 and a method according to claim 4, characterised in that
- whole blood is separated into distinct fractions of packed red blood cells, platelet-poor plasma, platelet-rich plasma and mononuclear cells;
- thereby the process is operated under process conditions to retain platelets and mononuclear cells in the separation chamber whilst allowing for the removal of platelet-poor plasma […];
- the platelet-poor plasma is collected in a first container and subsequently used for diluting the collected mononuclear cells in a second container […];
- the platelet-rich plasma is a) removed in turn under conditions to retain mononuclear cells in the separation chamber; and b) eliminated from the process through a path that bypasses both the container for the platelet-poor plasma and the container for the mononuclear cells […].
[3.6] The appellant argued that the technical problem set out above is successfully solved by the claimed system and method, because only platelet-poor plasma is used to dilute the collected mononuclear cells to the desired concentration, thereby avoiding the contamination of the mononuclear cells with platelets […].
[3.7] In the absence of any evidence to the contrary, the board accepts this explanation. In particular, it is plausible to the board that the separation of the plasma into two fractions under the specific conditions set out in claim 1, namely into a platelet-rich plasma fraction and a platelet-poor plasma fraction, allows for the use of the platelet-poor plasma thus obtained for the purpose of diluting the mononuclear cells. Thus, the level of platelets in the diluted mononuclear cell product will be low. Moreover, contamination of the mononuclear cells with red blood cells is prevented by removing the latter from both the platelet constituents and the mononuclear cells […]. Therefore, the resulting product will be in a relatively pure state. Therefore, the board is satisfied that the technical problem posed is solved by the claimed subject-matter.
[3.8] It remains to be decided whether the claimed solution is obvious having regard to the prior art.
[3.8.1] In the blood processing system and method according to D1, the mononuclear cells are accumulated behind a barrier and, once a sufficient volume of the mononuclear cells has accumulated, they are caused to spill over the barrier into a collection well […]. During the period in which mononuclear cells are being accumulated, both platelets and plasma flow continuously past the barrier. The platelets accumulate in a well beyond the barrier. Subsequently they are removed from the blood processing system through a collect line and returned to the donor. The remaining platelet-poor plasma is collected by another collect line […]. During the collection of mononuclear cells, platelet-poor plasma is also collected at the plasma exit port […]. In the blood processing system and method of D1, platelet-poor plasma is never collected whilst both platelets and mononuclear cells are retained in the separation chamber. According to D1 platelets and platelet-poor plasma are both collected continuously whilst the mononuclear cells are being accumulated during the accumulation phase […].
[3.8.2] The board agrees with the appellant’s argument according to which nothing in D1 provides an incentive to operate under specific process conditions to retain platelets and mononuclear cells in the separation chamber whilst allowing for the removal of platelet-poor plasma.
[3.8.3] The board is aware of the statement contained in D1, according to which “it may also be desirable to collect some plasma in order to dilute the white blood cell collection to a desired volume before freezing it” […]. In the board’s view this statement confirms what is already known from the general technical knowledge of the skilled person, namely that plasma is a suitable diluent for the “white blood cell collection”, i.e. blood fractions containing mononuclear cells. In view of the fact that the statement referred to above is of a very general nature, it cannot be regarded as a pointer towards the solution of the technical problem underlying the present invention.
[3.8.4] It follows from the above that the disclosure of D1 does not provide the skilled person with an incentive to look for the claimed system and method in order to solve the technical problem posed.
[3.9] The board concludes, therefore, that the subject-matter of independent claims 1 and 4, respectively, involves an inventive step as required by A 52(1) and A 56.
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