Cell

1. A T cell or natural killer (NK) cell which co-expresses a first chimeric antigen receptor (CAR) and second CAR at the cell surface, each CAR comprising:

(i) an antigen-binding domain;

(ii) a spacer

(iii) a trans-membrane domain; and

(iv) an endodomain

wherein the antigen binding domains of the first and second CARs bind to different antigens,

wherein the spacer of the first CAR is different from the spacer of the second CAR such that when both first and second CARs bind their target antigen, the difference in spacer dimensions results in spatial separation of the activating and inhibitory CARs to different parts of the membrane,

wherein one of the first or second CARs is an activating CAR comprising an activating endodomain and the other CAR is an inhibitory CAR comprising a ligation-off inhibitory endodomain, and

wherein the ligation-off inhibitory endodomain comprises a CD148 or CD45 tyrosine phosphatase domain.

2. The T or NK cell according to claim 1 , wherein either the first spacer or the second spacer comprises a CD8 stalk and the other spacer comprises the hinge, CH2 and CH3 domain of IgG-I.

3. The T or NK cell according to claim 1 , wherein the antigen-binding domain of the first CAR binds CD5 and the antigen-binding domain of the second CAR binds CD19.

4. A nucleic acid sequence encoding both first and second chimeric antigen receptors (CARs) as defined in claim 1 .

5. The nucleic acid sequence according to claim 4 , which has the following structure:

AgB1-spacer1-TM1-endo1-coexpr-AbB2-spacer2-TM2-endo2 in which AgB1 is a nucleic acid sequence encoding the antigen-binding domain of the first CAR;

spacer 1 is a nucleic acid sequence encoding the spacer of the first CAR;

TM1 is a a nucleic acid sequence encoding the transmembrane domain of the first CAR;

endo 1 is a nucleic acid sequence encoding the endodomain of the first CAR;

coexpr is a nucleic acid sequence enabling co-expression of both CARs

AgB2 is a nucleic acid sequence encoding the antigen-binding domain of the second CAR;

spacer 2 is a nucleic acid sequence encoding the spacer of the second CAR;

TM2 is a a nucleic acid sequence encoding the transmembrane domain of the second CAR;

endo 2 is a nucleic acid sequence encoding the endodomain of the second CAR;

which nucleic acid sequence, when expressed in a T cell, encodes a polypeptide which is cleaved at the cleavage site such that the first and second CARs are co-expressed at the T cell surface.

6. The nucleic acid sequence according to claim 5 , wherein coexpr encodes a sequence comprising a self-cleaving peptide.

7. The nucleic acid sequence according to claim 5 , wherein alternative codons are used in regions of sequence encoding the same or similar amino acid sequences, in order to avoid homologous recombination.

8. A kit which comprises

(i) a first nucleic acid sequence encoding the first chimeric antigen receptor (CAR) as defined in claim 1 , which nucleic acid sequence has the following structure: AgB1-spacer1-TM1-endo1 in which

AgB1 is a nucleic acid sequence encoding the antigen-binding domain of the first CAR;

spacer 1 is a nucleic acid sequence encoding the spacer of the first CAR;

TM1 is a nucleic acid sequence encoding the transmembrane domain of the first CAR;

endo 1 is a nucleic acid sequence encoding the endodomain of the first CAR; and

(ii) a second nucleic acid sequence encoding the second chimeric antigen receptor (CAR) as defined in claim 1 , which nucleic acid sequence has the following structure:

AgB2-spacer2-TM2-endo2

AgB2 is a nucleic acid sequence encoding the antigen-binding domain of the second CAR;

spacer 2 is a nucleic acid sequence encoding the spacer of the second CAR;

TM2 is a a nucleic acid sequence encoding the transmembrane domain of the second CAR;

endo 2 is a nucleic acid sequence encoding the endodomain of the second CAR.

9. The kit comprising: a first vector which comprises the first nucleic acid sequence as defined in claim 8 ; and a second vector which comprises the first nucleic acid sequence as defined in claim 8 .

10. A vector comprising a nucleic acid sequence according to claim 4 .

11. The vector according to claim 10 which is a retroviral vector or a lentiviral vector or a transposon.

12. A method for making a T or NK cell according to claim 1 , which comprises the step of introducing: a nucleic acid sequence according to claim 4 ; a first nucleic acid sequence and a second nucleic acid sequence as defined in claim 8 ; and/or a first vector and a second vector as defined in claim 9 , or a vector according to claim 10 , into a T or NK cell.

13. The method according to claim 12 , wherein the T or NK cell is from a sample isolated from a subject.

14. A pharmaceutical composition comprising a plurality of T or NK cells according to claim 1 .

15. A method for treating a cancer, which comprises the step of administering a pharmaceutical composition according to claim 14 to a subject.

16. The method according to claim 15 , which comprises the following steps:

(i) isolation of a T cell-containing sample from a subject;

(ii) transduction or transfection of the T cells with: a nucleic acid sequence according to claim 4 ; a first nucleic acid sequence and a second nucleic acid sequence as defined in claim 8 ; a first vector and a second vector as defined in claim 9 or a vector according to claim 10 ; and

(iii) administering the T cells from (ii) to the subject.