Systems, methods, and devices for blood treatment

1. A method of performing photopheresis, comprising:

arranging leukocytes in blood from a living animal by creating a flow of the blood that generates a shear profile that causes leukocytes to be concentrated in a fraction of the flow;

illuminating the leukocytes in the fraction of the flow; and

returning the illuminated leukocytes to the living animal,

wherein the creating a flow of blood includes flowing the blood in a separation channel having a cross-section in a plane perpendicular to a direction of the flow, and the cross-section has an aspect ratio greater than 10 and a minimum dimension less than 200 μm,

wherein the illuminating includes using a therapeutic light source positioned so as to illuminate the concentrated leukocytes in the fraction of the flow in the separation channel without passing through a layer of erythrocytes in the separation channel.

2. The method of claim 1 , wherein the flow is laminar.

3. The method of claim 1 , wherein the illuminating includes generating light having a significant portion of its energy in the 200-400 nm wavelength range.

4. The method of claim 1 , wherein the illuminating includes shining light on transparent walls of a channel containing the flow.

5. The method of claim 1 , wherein the creating a flow of blood is such that erythrocytes in the flowing blood are at least partially shielded by the concentrated leukocytes from the illuminating.

6. The method of claim 1 , wherein the flow of the blood is in a channel enclosed by a housing, and the therapeutic light source is positioned within said housing to illuminate the concentrated leukocytes in said channel.

7. The method of claim 1 , wherein the illuminating includes directing light from the therapeutic light source onto one or more channels containing the flow of blood, the flowing in each channel being such that the concentrated leukocytes are between a wall of the channel and a layer of erythrocytes.

8. The method of claim 7 , wherein the therapeutic light source and at least an illuminated portion of the one or more channels are enclosed in a common housing, and internal surfaces of the common housing are reflective.

9. The method of claim 7 , wherein the illuminating includes using one or more optical elements in an illumination path between the therapeutic light source and the one or more channels so as to concentrate light from the source onto respective illuminated portions of the channels.

10. The method of claim 7 , wherein the illuminating includes using one or more optical elements in an illumination path between the therapeutic light source and the one or more channels so as to uniformly illuminate respective illuminated portions of the channels.

11. The method of claim 1 , wherein the illuminating includes directing light from one or more therapeutic light sources onto multiple channels, each channel containing a respective flow of blood.

12. The method of claim 11 , wherein the multiple channels are arrayed with respect to each other such that light from the one or more therapeutic light sources illuminates concentrated leukocytes in each channel while erythrocytes in each channel are at least partially shielded from illumination.

13. The method of claim 1 , wherein the creating a flow of the blood includes concentrating leukocytes in the fraction of the flow without removing other components from the blood.

14. A method of performing a photopheresis treatment on a patient, comprising:

flowing whole blood from the patient through a channel such that a shear profile causes leukocytes in the whole blood to segregate from other blood components flowing in the channel, the leukocytes being arranged in the flow between the other blood components and a wall of the channel in a cross-flow direction; and

at a same time as said flowing whole blood, illuminating with ultraviolet light through said wall of the channel the leukocytes in the flow while in the presence of the other blood components, the illuminating being sufficient to deliver a medically effective dose of ultraviolet light for said photopheresis treatment,

wherein the flow in the channel is laminar,

the channel has a minimum cross-flow dimension of less than 200 μm and a cross-section in a plane perpendicular to a direction of the flow, and

said cross-section has an aspect ratio greater than 10.

15. The method of claim 14 , wherein said channel is in a portable treatment module worn by the patient.

16. The method of claim 14 , further comprising conveying the illuminated leukocytes and the other blood components to the patient via a blood line directly connecting an outlet of the channel to an access of the patient.

17. The method of claim 14 , further comprising, at a same time as the flowing whole blood, pumping sheathing fluid into the channel through a sheathing fluid inlet so as to flow in a same direction as the blood flow and to be between the leukocytes and the wall of the channel in the cross-flow direction.

18. The method of claim 17 , further comprising, withdrawing the sheathing fluid from the channel through a sheathing fluid outlet having a filter member, the filter member being constructed to prevent leukocytes and erythrocytes from leaving the channel through said sheathing fluid outlet.