A combination of compositions for use in immunotherapy for reducing side-effects of an antigen-recognizing receptor expressed on the cell membrane of immune effector cells against antigen-expressing non-target cells in an individual, comprising a) said antigen-recognizing receptor expressed on the cell membrane of immune effector cells wherein said antigen-recognizing receptor specifically recognizes an antigen on target cells in said individual; b) hematopoietic cells resistant to recognition of said antigen by said antigen-recognizing receptor, wherein said hematopoietic cells have a deviation in said antigen, and wherein said antigen having said deviation i) has at least one splice variant within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains, or ii) has at least a natural polymorphic form within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains; or iii) is modified to a non-natural polymorphic form within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains, wherein said non-natural polymorphic form does not alter or affect the natural function of said antigen on the cells; or iv) is deleted without alteration or affecting the natural function of the hematopoietic cell, wherein said antigen is expressed on target cells in said individual and at least on one hematopoietic cell type of said individual. a) said antigen-recognizing receptor expressed on the cell membrane of immune effector cells wherein said antigen-recognizing receptor specifically recognizes an antigen on target cells in said individual; b) hematopoietic cells resistant to recognition of said antigen by said antigen-recognizing receptor, wherein said hematopoietic cells have a deviation in said antigen, and wherein said antigen having said deviation i) has at least one splice variant within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains, or ii) has at least a natural polymorphic form within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains; or iii) is modified to a non-natural polymorphic form within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains, wherein said non-natural polymorphic form does not alter or affect the natural function of said antigen on the cells; or iv) is deleted without alteration or affecting the natural function of the hematopoietic cell, wherein said antigen is expressed on target cells in said individual and at least on one hematopoietic cell type of said individual. i) has at least one splice variant within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains, or ii) has at least a natural polymorphic form within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains; or iii) is modified to a non-natural polymorphic form within the extracellular domain of said antigen suitable for generating different epitopes for antigen binding domains, wherein said non-natural polymorphic form does not alter or affect the natural function of said antigen on the cells; or iv) is deleted without alteration or affecting the natural function of the hematopoietic cell, wherein said antigen is expressed on target cells in said individual and at least on one hematopoietic cell type of said individual.