A method for identifying a peptide antigen which is relevant to a human or veterinary non-autoimmune disease involving T cell activation, said method comprising the following steps: (i) contacting a first biological fluid sample containing IgG immunoglobulins from a first non-human animal affected by the non-autoimmune disease with a microarray comprising a plurality of isolated or synthesized antigenic peptides, each peptide having a pre-determined location in the microarray and comprising an amino acid sequence of a protein from the non-human animal; (ii) detecting the binding of one or more of the IgG immunoglobulins present in the first sample with one or more of the antigenic peptides in the microarray to provide a first IgG-bound peptide profile; (iii) comparing the first IgG-bound peptide profile to a second IgG-bound peptide profile generated by contacting a microarray as defined in step (i) with a second biological fluid sample containing IgG immunoglobulins from a second non-human animal, wherein the second non-human animal is not affected by the non-autoimmune disease and wherein the first and second non-human animals belong to the same species and are congenic animals; (iv) identifying the one or more IgG-bound peptides which are present in the first IgG-binding profile and are not present in the second IgG binding profile; (v) querying a database of animal protein sequences using the amino acid sequence of each IgG-bound peptide identified in step (iv) as the query in order to select one or more animal proteins comprising a peptide sequence which has an amino acid sequence identity to the amino acid sequence of each of the queried peptides comprised between 67% and 100%, wherein the animal protein sequences are from an animal belonging to a species which is different from the first and second non-human animals of step (iii); (vi) identifying as peptide antigens relevant to the non-autoimmune disease the peptide sequences which have from 67% to 100% amino acid sequence identity selected in step (v) and which are comprised of an animal protein expressed in a tissue affected by the non-autoimmune disease wherein the first and second non-human animals are mice and the first non-human animal is a mouse model of the disease, wherein the non-autoimmune disease is selected from the group consisting of heart failure, cardiac diseases, vascular diseases, atherosclerosis, vascular stenosis, non-type 1 diabetes, metabolic syndrome, obesity, Amyotrophic Lateral Sclerosis-ALS, Alzheimer's Disease, Dementia, Age-related Dementia, Mild Cognitive Decline, Parkinson's Disease, and any combination thereof. (i) contacting a first biological fluid sample containing IgG immunoglobulins from a first non-human animal affected by the non-autoimmune disease with a microarray comprising a plurality of isolated or synthesized antigenic peptides, each peptide having a pre-determined location in the microarray and comprising an amino acid sequence of a protein from the non-human animal; (ii) detecting the binding of one or more of the IgG immunoglobulins present in the first sample with one or more of the antigenic peptides in the microarray to provide a first IgG-bound peptide profile; (iii) comparing the first IgG-bound peptide profile to a second IgG-bound peptide profile generated by contacting a microarray as defined in step (i) with a second biological fluid sample containing IgG immunoglobulins from a second non-human animal, wherein the second non-human animal is not affected by the non-autoimmune disease and wherein the first and second non-human animals belong to the same species and are congenic animals; (iv) identifying the one or more IgG-bound peptides which are present in the first IgG-binding profile and are not present in the second IgG binding profile; (v) querying a database of animal protein sequences using the amino acid sequence of each IgG-bound peptide identified in step (iv) as the query in order to select one or more animal proteins comprising a peptide sequence which has an amino acid sequence identity to the amino acid sequence of each of the queried peptides comprised between 67% and 100%, wherein the animal protein sequences are from an animal belonging to a species which is different from the first and second non-human animals of step (iii); (vi) identifying as peptide antigens relevant to the non-autoimmune disease the peptide sequences which have from 67% to 100% amino acid sequence identity selected in step (v) and which are comprised of an animal protein expressed in a tissue affected by the non-autoimmune disease wherein the first and second non-human animals are mice and the first non-human animal is a mouse model of the disease, wherein the non-autoimmune disease is selected from the group consisting of heart failure, cardiac diseases, vascular diseases, atherosclerosis, vascular stenosis, non-type 1 diabetes, metabolic syndrome, obesity, Amyotrophic Lateral Sclerosis-ALS, Alzheimer's Disease, Dementia, Age-related Dementia, Mild Cognitive Decline, Parkinson's Disease, and any combination thereof.