What’s the Difference Between Monocytes and Lymphocytes?

• Monocytes are responsible for detecting and killing pathogens, while lymphocytes make antibodies to target specific antigens.
• Lymphocytes are smaller than monocytes and make up a larger proportion of white blood cells in your body.
• Monocytes are either macrophages or dendritic cells. Lymphocytes can be B cells, T cells, or natural killer cells.

Monocyte and Lymphocyte Overview

The major difference between these cells is their function. Both monocytes and lymphocytes are types of leukocytes, or white blood cells. These white blood cells both patrol your immune system for antigens, or foreign molecules on pathogens like viruses and bacteria. When they find antigens, they fight them off. Monocytes do this by directly killing antigens, while lymphocytes target them with antibodies, or special proteins that neutralize antigens.

Differences Between Monocytes and Lymphocytes

Function When monocytes find antigens in your blood and tissues, they envelop the pathogen and kill them in a process called phagocytosis. Instead of directly killing antigens, lymphocytes create antibodies that attach to specific antigens. They then send out the antibodies which neutralize the antigens. During phagocytosis, monocytes essentially eat and consume the pathogen.

Immunity Your body has 2 immune responses: innate and adaptive. When an antigen enters your body, monocytes immediately respond to the invader and kill them; this is the innate response. The adaptive immune response is slower and more specialized. Lymphocytes identify and target the antigens with individualized antibodies. They then form a memory of the antigen so if it infects you again later, the adaptive response is quicker and more efficient. Basically, monocytes are like first responders that respond quickly and non-specifically to antigens. Lymphocytes are like specialized back-ups that operate more slowly. They typically take over when monocytes aren’t killing the antigens effectively. Lymphocytes are the reason why you can only get some diseases once, like chicken pox, or why secondary infections are milder.

Size Lymphocytes are smaller than monocytes. Your red blood cells are pretty small, and lymphocytes are only the tiniest bit bigger. On the other hand, monocytes are about twice as big as red blood cells. They’re also the largest white blood cell, typically making them the easiest to identify, too. Reactive or atypical lymphocytes are large lymphocytes. They typically transform and enlarge when they sense and respond to antigens.

Abundance There are fewer monocytes in your body than lymphocytes. Monocytes make up about 2-8% of all the white blood cells in your body. Lymphocytes make up a larger proportion, accounting for 20-40% of all the white blood cells in your system. Lymphocytes are typically the second most populous white blood cell in your body. They come in after neutrophils, which are the most abundant white blood cells in your body.

Nucleus One of the other distinguishing factors between lymphocytes and monocytes is their nucleus shape. Lymphocytes have an identifiably large and round nucleus. A monocyte’s nucleus is also pretty unique. It has a distinct U-shape, often looking like a kidney bean. The nucleus is a rounded structure that typically rests in the middle of a cell. It functions as the cell’s control center and contains genetic information like DNA and RNA. When you stain monocytes and lymphocytes in a blood smear, it’s easy to tell that they’re different. While they both have a light blue cytoplasm, which is the fluid inside a cell, and a deep purple nucleus, the different shape of the nucleus is very apparent.

Types Monocytes are either macrophages or dendritic cells. These 2 types of monocytes work to kill pathogens and ask for help from other white blood cells. Lymphocytes come in 3 varieties: B cells, T cells, and natural killer cells. These lymphocytes make antibodies and work with monocytes to destroy pathogens.

Formation Both lymphocytes and monocytes develop in your bone marrow. There, lymphocytes come from lymphoblasts, which are immature cells. On the other hand, monocytes are derived from immature cells called monoblasts. When lymphoblasts and monoblasts mature into lymphocytes and monocytes, respectively, both of these white blood cells leave your bone marrow and travel through your bloodstream and tissues.

Lifespan Monocytes have shorter life cycles than lymphocytes. Most of these cells only circulate in your system for 1 to 3 days. Lymphocytes tend to stay in your system for a few weeks to several months. Some lymphocytes circulate your body for your entire lifetime.

What are monocytes?

Monocytes are your first line of defense to kill pathogens. As the first responders in your immune system, monocytes use their receptors to detect when antigens enter your body. They quickly move through your blood to find the affected tissues, where they either eat the harmful pathogen or call for backup. The 2 types of monocytes that take on these roles: Macrophages: these monocytes are responsible for eating pathogens through phagocytosis. They engulf the pathogen and remove the toxic enzymes inside. They then remove these dead cells from your body. Dendritic cells: these monocytes alert other white blood cells to the presence of pathogens. They take antigens from the pathogen, which helps other white blood cells form neutralizing antibodies, and release cytokines to show the white blood cells where to find the pathogen.

What are lymphocytes?

Lymphocytes create antibodies and remember pathogens. These white blood cells also kill pathogens, but they take their time doing so. Lymphocytes find out how to destroy them by creating antibodies, a type of protein that specifically targets certain antigens. They then catalog the pathogens so they’re prepared the next time they enter your body. The 3 different types of lymphocytes share these responsibilities: B cells: these lymphocytes make antibodies. They secrete the antibodies to cover pathogens, which marks them to be killed. T cells: these are either cytotoxic T cells or helper T cells. Cytotoxic T cells directly kill pathogens, working alongside macrophages. Helper T cells draw more macrophages to the area by distributing cytokines. Natural killer cells: these lymphocytes use enzymes to target and kill tumor cells.