• The C-terminal variable region of the mycoplasma variable surface antigen (Vsa) proteins contains up to 60 tandem repeat units, and this variable length proves a major factor affecting adherence properties and shielding these bacteria from host immune responses. • The cell-surface Vsa proteins constitute as much as 10% of total mycoplasma protein, helping to shield cells against environmental factors. • When grown on solid surfaces and producing short Vsa proteins, M. pulmonis forms biofilms that confer partial resistance to immune system components. • Mycoplasmas form biofilm-like aggregates on host tissues, where they might also form tower structures to protect against innate immune system responses.
