Optimal MHC-II-restricted tumor antigen presentation to CD4+ T helper cells: the key issue for development of anti-tumor vaccines

Table 1 Major elements influencing tumor escape from adaptive immune recognition and destruction

1. Tumor-related
- Insufficient tumor antigen expression
- Loss of MHC class I expression by tumor
- Lack of MHC class II expression by tumor
- Production of immunosuppressive factors for T and B cells
2. Immune cells-related
- Insufficient lymphocyte penetration into the tumor tissue
- Lack of T cell help
Insufficient MHC-II-restricted antigen presentation
Insufficient TH triggering
- Lack or insufficient CTL activity
Insufficient MHC-I-restricted antigen presentation
Insufficient support by TH cells
Scarce lytic activity
- Extrinsic functional blocking of T cells
Regulatory and suppressor cells
Inhibitory cytokines

ISSN: 1479-5876