Which cytoplasmic organelles are described as having a "tennis-racket" shape and are found in Langerhans cells?

Birbeck granules are specialized cytoplasmic organelles found predominantly in Langerhans cells, which are a type of dendritic cell involved in immune responses. These organelles are characterized by their distinctive “tennis-racket” shape, which is a result of their elongated structure and the presence of an internal structure resembling a racquet.

The significance of Birbeck granules lies in their function as part of the antigen-processing and presentation pathway. Langerhans cells capture and process antigens and then present them to T cells, a critical step in initiating an immune response. The presence of Birbeck granules indicates the specialized nature of Langerhans cells as they contribute to the body's immune surveillance.

The other organelles listed do not have this unique morphology or specific associations with Langerhans cells. Phagosomes, lysosomes, and endosomes are involved in various cellular processes such as digestion and recycling of cellular materials, but they do not exhibit the characteristic shape or function associated with Birbeck granules.