T helper cells are classified as which of the following?

T helper cells are classified as CD4+ because they specifically express the CD4 glycoprotein on their surface. This marker is crucial for their function in the immune response. CD4+ T helper cells play a vital role in the adaptive immune system by assisting other immune cells, such as B cells and CD8+ cytotoxic T cells, enhancing the overall immune response to pathogens.

In contrast, CD8+ cells are primarily associated with cytotoxic T lymphocytes, which are responsible for killing infected or cancerous cells, and do not participate in the helper functions attributed to CD4+ T cells. CD44 and CD55 are different surface markers associated with various immune functions and cell adhesion but do not classify T helper cells. Thus, the presence of CD4 defines T helper cells and is a key aspect of their identification and functionality within the immune system.