The 'protein traffic hypothesis' suggests that the inflammation associated with autoimmune disease, trauma and disturbances of blood circulation is the result of misguided protein trafficking. The hypothesis divides the antigen spectrum into an intracellular component and an extracellular component. While the intracellular component is recognised by MHC class-I molecules and is presented to CD8 T-lymphocytes, the extracellular component is recognised by MHC class-II molecules and is presented to CD4 T-lymphocytes. To test this hypothesis, CD4 and CD8 T-cell counts of 271 HIV-negative patients of the University Hospital, Mainz, Germany were examined retrospectively. The results corroborate the observation that patients with autoimmune disease have a low CD4/CD8-ratio (0.5-1), while patients with acute infarction have a higher CD4/CD8-ratio (3-5). The normal CD4/CD8-ratio is 1.2-1.4. The results of this study confirm previous reports on the protein traffic hypothesis. Our data suggests that the CD4/CD8-ratio has broad clinical applications.